CATALYST FOR POLYMERIZATION OF CYCLIC ETHER AND CYCLIC ESTER MONOMERS AND THE RESULTING POLYMERS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to US Provisional Application No. 63/355,237 filed June 24, 2022, the disclosure of which is incorporated herein by reference. [0002] The present disclosure generally relates to ring-opening polymerization and more specifically relates to catalyst complexes useful in polymerizing lactones, particularly β-lactones to produce biodegradable polymer.

BACKGROUND

[0003] Ring-opening polymerization (“ROP”) of cyclic ethers and esters produces polyethers and polyesters that can potentially be biodegradable and/or recyclable back to monomers or monomer units. Among the cyclic ethers and esters, β-lactones such as β-propiolactone and β-butyrolaetone have sign ificant importance because polyhydroxybutyrate (“PHB”), a biodegradable polymer, can be produced from (3-lactones.

[0004] Although various catalysts and methods to polymerize β-butyrolactone have been previously described, commercially viable catalysts for polymerization of β-lactones have not been developed. Reasons for the lack of such catalysts include the cost of the metal/metal precursors and/or lack of availability of certain metals as well as the requirement that the catalyst must operate at industrially irrelevant conditions (low temperature etc.).

SUMMARY

[0005] Provided herein are methods of ring-opening polymerization of β-lactones using a catalyst complex of the structural Formula HI wherein n = 0, 1 and R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl. Further, R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl and R ² and R ³ may be joined to form a fused aromatic ring system. In addition, R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline. M is Zn and Al and each L is bis(trimethylsilyl)amine, methyl and ethyl. Moreover, x is an integer between 1 and 3 the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent.

[0006] Also provided herein are methods of making a polyhydroxyalkanote (PHA) polymer by ring- opening polymerization comprising the steps of polymerizing a lactone in the presence of a solvent and the catalyst complex of the structural Formula HI.

[0007] These and other features and attributes of the disclosed catalyst complexes and methods of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.

BRIEF DESCRIPTION OF DRAWINGS

[0008] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:

[0009] FIG. 1A shows the ¹³ C NMR spectra (methylene carbon region) of poly-(0- hydroxybutyrate)s obtained by polymerization of (R,S)-|3-butyrolactone initiated with 18-crown-6 supramolecular complexes of potassium methoxide at 20°C. Jedlinski et al., Macromolecules, v.29(l l), 1996, Figure 2a.

[0010] FIG. IB shows the ¹³ C NMR spectra (methylene carbon region) of poly-(0- hydroxybutyrate)s obtained by polymerization of (R,S)-|3-butyrolactone initiated with 18-crown-6 supramolecular complexes of potassium methoxide at -10°C. Jedlinski et al., Macromolecules, v.29(l l), 1996, Figure 2b.

[0011] FIG. 2A shows the differential scanning calorimetry (“DSC”) data for the polymer of Example 24.

[0012] FIG. 2B shows the DSC data for the polymer of Example 25.

[0013] FIG. 3A shows the ¹³ C NMR spectra (methylene carbon region) for the polymer of

Example 20.

[0014] FIG. 3B shows the ¹³ C NMR spectra (methylene carbon region) for the polymer of Example 21.

[0015] FIG. 3C shows the ¹³ C NMR spectra (methylene carbon region) for the polymer of Example 22.

[0016] FIG. 3D shows the ¹³ C NMR spectra (methylene carbon region) for the polymer of Example 23.

[0017] FIG. 4 A shows the ¹³ C NMR spectra (carbonyl region) for the polymer of Example 20.

[0018] FIG. 4B shows the ¹³ C NMR spectra (carbonyl region) for the polymer of Example 21. [0019] FIG. 4C shows the ¹³ C NMR spectra (carbonyl region) for the polymer of Example 22.

[0020] FIG. 4D shows the ¹³ C NMR spectra (carbonyl region) for the polymer of Example 23.

[0021] FIG. 5A shows the DSC data for the polymer of Example 20.

[0022] FIG. 5B shows the DSC data for the polymer of Example 21.

[0023] FIG. 5C shows the DSC data for the polymer of Example 22.

[0024] FIG. 5D shows the DSC data for the polymer of Example 23.

[0025] FIG. 6 shows the ¹³ C NMR spectra (carbonyl region) for the polymer of Example 26.

DETAILED DESCRIPTION

[0026] The present catalyst complexes are useful in polymerization processes which operate at higher temperatures (i.e., above room temperature) and contain metals that are abundant and have low toxicity.

Definitions

[0027] The term "alkenyl" means a straight-chain, branched-chain, or cyclic hydrocarbon radical having one or more double bonds. These alkenyl radicals may be optionally substituted. Examples of suitable alkenyl radicals include ethenyl, propenyl, allyl, 1,4-butadienyl cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cyclooctenyl, including their substituted analogues.

[0028] The term "alkyl" as used herein refers to a branched or unbranched saturated hydrocarbon group having 1 to about 50 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, octyl, decyl, and the like, as well as cycloalkyl groups such as cyclopentyl, cyclohexyl and the like. Generally, alkyl groups contain 1 to about 20 carbon atoms.

[0029] The term "alkoxy" or "alkoxide" means an alkyl ether radical wherein the term alkyl is as defined above. Examples of suitable alkyl ether radicals include methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, iso-butoxy, sec-butoxy, tert-butoxy, and phenoxyl.

[0030] The term "alkynyl" as used herein refers to a branched or unbranched, cyclic or acyclic hydrocarbon group containing 2 to about 50 carbon atoms and at least one triple bond, such as ethynyl, n-propynyl, isopropynyl, n-butynyl, isobutynyl, octynyl, decynyl, and the like. Generally, alkynyl groups herein may have 2 to about 20 carbon atoms.

[0031] Where isomers of a named alkyl, alkenyl, alkoxide, or aryl group exist (e.g., n-butyl, iso-butyl, iso-butyl, and tert-butyl) reference to one member of the group (e.g., n-butyl) shall expressly disclose the remaining isomers (e.g., iso-butyl, sec-butyl, and tert-butyl) in the family. Likewise, reference to an alkyl, alkenyl, alkoxide, or aryl group without specifying a particular isomer (e.g., butyl) expressly discloses all isomers (e.g., n-butyl, iso-butyl, sec-butyl, and tert-butyl).

[0032] An "anionic leaving group" is a negatively charged group that donates one or more pairs of electrons to a metal ion, that can be displaced by monomer or activator.

[0033] An "anionic ligand" is a negatively charged ligand that donates one or more pairs of electrons to a metal ion. A "neutral donor ligand" is a neutrally charged ligand which donates one or more pairs of electrons to a metal ion.

[0034] The term "aromatic" is used in its usual sense, including unsaturation delocalized across several bonds around a ring. The term "aryl" as used herein refers to a group containing an aromatic ring. Aryl groups herein include groups containing a single aromatic ring or multiple aromatic rings that are fused together, linked covalently, or linked to a common group such as a methylene or ethylene moiety. More specific aryl groups contain one aromatic ring or two or three fused or linked aromatic rings, e.g., phenyl, naphthyl, biphenyl, anthracenyl, or phenanthrenyl. In particular embodiments, aryl substituents include 1 to about 200 atoms other than hydrogen, typically 1 to about 50 atoms other than hydrogen, and specifically 1 to about 20 atoms other than hydrogen. In some embodiments herein, multi-ring moieties are substituents and in such embodiments the multi-ring moiety can be attached at an appropriate atom. For example, "naphthyl" can be 1 -naphthyl or 2-naphthyl; "anthracenyl" can be

1 -anthracenyl, 2 -anthracenyl or 9-anthracenyl; and "phenanthrenyl" can be 1 -phenanthrenyl,

2-phenanthrenyl, 3 -phenanthrenyl, 4-phenanthrenyl or 9-phenanthrenyl.

[0035] The term “aromatic ring” is a cyclic structure containing conjugated pi bonds with unhybridized p orbitals that overlap to form a continuous loop resulting in a lower energy due to delocalization of electons.

[0036] The term "aryl" or "aryl group" means a carbon-containing aromatic ring and the substituted variants thereof can include phenyl, 2-methyl-phenyl, xylyl, 4-bromo-xylyl. Likewise, heteroaryl means an aryl group where a ring carbon atom (or two or three ring carbon atoms) has been replaced with a heteroatom, such as N, O, or S. As used herein, the term "aromatic" also refers to pseudoaromatic heterocycles which are heterocyclic substituents that have similar properties and structures (nearly planar) to aromatic heterocyclic ligands, but are not by definition aromatic; likewise, the term aromatic also refers to substituted aromatics.

[0037] The terms "aryloxy" and "aryloxide" mean an aryl group bound to an oxygen atom, such as an aryl ether group/radical connected to an oxygen atom and can include those where the aryl group is a Ci to Cio hydrocarbyl. Examples of suitable aryloxy radicals can include phenoxy, and the like.

[0038] As used herein, a "catalyst" includes a single catalyst, or multiple catalysts. Catalysts can have isomeric forms such as conformational isomers or configurational isomers. Conformational isomers include, for example, conformers and retainers. Configurational isomers include, for example, stereoisomers.

[0039] The term "complex," may also be referred to as catalyst precursor, precatalyst, catalyst, catalyst compound, transition metal compound, or transition metal complex. These words are used interchangeably. Activator and cocatalyst are also used interchangeably.

[0040] Herein, "catalyst" and "catalyst complex" are used interchangeably.

[0041] As used herein, a "catalyst system" includes at least one catalyst compound and an activator. A catalyst system of the present disclosure can further include a support material and an optional co-activator. For the purposes of this disclosure, when a catalyst is described as including neutral stable forms of the components, it is well understood by one of ordinary skill in the art, that the ionic form of the component is the form that reacts with the monomers to produce polymers. Furthermore, catalysts of the present disclosure represented by a Formula are intended to embrace ionic forms thereof of the compounds in addition to the neutral stable forms of the compounds. Furthermore, activators of the present disclosure are intended to embrace ionic/reaction product forms thereof of the activator in addition to ionic or neutral form.

[0042] As used herein, where used, the phrase "characterized by the formula" is intended to comprise any compound that can be defined by such formula.

[0043] The terms "compound" and "complex" are generally used interchangeably in this specification, but those of skill in the art may recognize certain compounds as complexes and vice versa. For the purposes of illustration, representative certain groups are defined herein. These definitions are intended to supplement and illustrate, not preclude, the definitions known to those of skill in the art.

[0044] The term "continuous" means a system that operates without interruption or cessation. For example, a continuous process to produce a polymer would be one where the reactants are continually introduced into one or more reactors and polymer product is continually withdrawn during a polymerization process.

[0045] The terms "cyclo" and "cyclic" are used herein to refer to saturated or unsaturated radicals containing a single ring or multiple condensed rings. Suitable cyclic moieties include, for example, cyclopentyl, cyclohexyl, cyclooctenyl, bicyclooctyl, phenyl, naphthyl, pyrrolyl, furyl, thiophenyl, imidazolyl, and the like. In particular embodiments, cyclic moieties include between 3 and 200 atoms other than hydrogen, between 3 and 50 atoms other than hydrogen or between 3 and 20 atoms other than hydrogen.

[0046] As used herein, and unless otherwise specified, the term "Cn" means hydrocarbon(s) having n carbon atom(s) per molecule, where n is a positive integer. Likewise, a "C _m -C _y " group or compound refers to a group or compound comprising carbon atoms at a total number thereof in the range from m to y. Thus, a C1-C4 alkyl group refers to an alkyl group that includes carbon atoms at a total number thereof in the range of 1 to 4, e.g., 1.2.3 and 4.

[0047] By "divalent" as in "divalent hydrocarbyl", "divalent alkyl", "divalent aryl” and the like, is meant that the hydrocarbyl, alkyl, aryl or other moiety is bonded at two points to atoms, molecules or moieties with the two bonding points being covalent bonds.

[0048] The terms "group," "radical," and "substituent" are used interchangeably herein.

[0049] The terms "halo" and "halogen" are used in the conventional sense to refer to a chloro, bromo, fluoro or iodo radical.

[0050] More generally, the modifiers "hetero" and "heteroatom-containing", as in "heteroalkyl" or "heteroatom-containing hydrocarbyl group" refer to a molecule or molecular fragment in which one or more carbon atoms is replaced with a heteroatom. Thus, for example, the term "heteroalkyl" refers to an alkyl substituent that is heteroatom-containing. When the term "hcteroatom-containing" introduces a list of possible heteroatom-containing groups, it is intended that the term apply to every member of that group. That is, the phrase "heteroatomcontaining alkyl, alkenyl and alkynyl" is to be interpreted as "heteroatom-containing alkyl, heteroatom-containing alkenyl and heteroatom-containing alkynyl."

[0051] The term "heteroaryl" refers to an aryl radical that includes one or more heteroatoms in the aromatic ring. Specific heteroaryl groups include groups containing heteroaromatic rings such as thiophene, pyrazine, isoxazolo, pyrazole, pyrrole, furan, thiazole, oxazole, imidazole, isothiazole, oxadiazole, triazole, and benzo-fused analogues of these rings, such as indole, carbazole, benzofuran, benzothiophene, benzimidiazole, benzthiazole, benzoxazoles, indazole and the like and isomers thereof, e.g., reverse isomers.

[0052] The terms "heterocycle" and "heterocyclic" refer to a cyclic radical, including ring- fused systems, including heteroaryl groups as defined below, in which one or more carbon atoms in a ring is replaced with a heteroatom - that is, an atom other than carbon, such as nitrogen, oxygen, sulfur, phosphorus, boron or silicon. Heterocycles and heterocyclic groups include saturated and unsaturated moieties, including heteroaryl groups as defined below. Specific examples of heterocycles include pyrrolidine, pyrroline, furan, tetrahydrofuran, thiophene, imidazole, oxazole, thiazole, indole, and the like, including any isomers of these. Additional heterocycles are described, for example, in Alan R. Katritzky, Handbook of Heterocyclic Chemistry Pergammon Press, 1985, and in Comprehensive Heterocyclic Chemistry, A.R. Katritzky et al., eds, Elsevier, 2d. ed., 1996. The term "metallocycle" refers to a heterocycle in which one or more of the h eteroatoms in the ring or rings is a metal.

[0053] A heterocyclic ring is a ring having a heteroatom in the ring structure as opposed to a heteroatom substituted ring where a hydrogen on a ring atom is replaced with a heteroatom. For example, tetrahydrofuran is a heterocyclic ring and 4-N,N-dimethylamino-phenyl is a heteroatom substituted ring.

[0054] A substituted heterocyclic ring is a heterocyclic ring where a hydrogen of one of the ring atoms is substituted, e.g., replaced with a hydrocarbyl, or a heteroatom containing group (as further described in the definition of "substituted" herein).

[0055] The term "hydrocarbyl" refers to hydrocarbyl radicals containing 1 to about 50 carbon atoms, specifically 1 to about 24 carbon atoms, most specifically 1 to about 16 carbon atoms, including branched or unbranched, cyclic or acyclic, saturated or unsaturated species, such as alkyl groups, alkenyl groups, aryl groups, and the like.

[0056] The terms "hydrocarbyl radical," "hydrocarbyl group," or "hydrocarbyl" may be used interchangeably and are defined to mean a group comprising hydrogen and carbon atoms. [0057] Preferred hydrocarbyls are Ci-Cioo radicals that may be linear, branched, or cyclic, and when cyclic, aromatic or non-aromatic. Examples of such radicals include, but are not limited to, alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl, hexyl, octyl cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl, and the like, aryl groups, such as phenyl, benzyl naphthyl, and the like.

[0058] Unless otherwise indicated, (e.g., the definition of "substituted hydrocarbyl"), the term "substituted" means that at least one hydrogen atom has been replaced with at least one non-hydrogen group, such as a hydrocarbyl group, a heteroatom, or a heteroatom containing group, such as halogen (such as Br, Cl, F or I) or at least one functional group such as -NR*2, -NR*-CO-R*, -OR*,*-O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR* ₂ , -PO-(OR*) ₂ , -O-PO-(OR*) ₂ , -ASR* ₂ , -SbR* ₂ , -SR*, -SO ₂ -(OR*) ₂ , -BR* ₂ , -SiR* ₃ , -GeR* ₃ , -SnR* ₃ , -PbR* ₃ , -(CH ₂ )q-SiR* ₃ , or a combination thereof, where q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure), or where at least one heteroatom has been inserted within a hydrocarbyl ring. [0059] The term "substituted hydrocarbyl" means a hydrocarbyl radical in which at least one hydrogen atom of the hydrocarbyl radical has been substituted with at least one heteroatom (such as halogen, e.g., Br, Cl, F or I) or heteroatom-containing group (such as a functional group, e.g., -NR*2, -NR*-CO-R*,-OR*,*-O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR* ₂ , -PO-(OR*) ₂ , -O-PO-(OR*) ₂ , -ASR*2, -SbR* ₂ , -SR*, -SO ₂ -(OR*) ₂ , -BR* ₂ , -SiR* ₃ , -GeR* ₃ , -SnR* ₃ , -PbR* ₃ , -(CH2)q-SiR* ₃ , and the like, where q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure), or where at least one heteroatom has been inserted within a hydrocarbyl ring.

[0060] The terms "hydrosilylcarbyl radical," "hydrosilylcarbyl group," or "hydrosilylcarbyl" interchangeably refers to a group consisting of hydrogen, carbon, and silicon atoms only. A hydrosilylcarbyl group can be saturated or unsaturated, linear or branched, cyclic or acyclic, aromatic or non-aromatic, and with the silicon atom being within and/or pendant to the cyclic/aromatic rings.

[0061] The term "silyl group," refers to a group comprising silicon atoms, such as a hydrosilylcarbyl group.

[0062] The term “imidazole” refers to an aromatic heterocycle compound including a general formula C3H2H4 where nitrogen atoms are non-adjacent.

[0063] As used herein, Mn is number average molecular weight, Mw is weight average molecular weight, and Mz is z average molecular weight, wt. % is weight percent, and mol % is mole percent. Molecular weight distribution (MWD), also referred to as polydispersity index (PDI), is defined to be Mw divided by Mn. Unless otherwise noted, all molecular weight units (e.g., Mw, Mn, Mz) are g/mol.

[0064] The following abbreviations may be used herein: Me is methyl, Ph is phenyl, Et is ethyl, Pr is propyl, iPr is isopropyl, n-Pr is normal propyl, cPr is cyclopropyl, Bu is butyl, i-Bu is isobutyl, sBu is secondary butyl, tBu is tertiary butyl, n-Bu is normal butyl, MAO is methylalumoxane, Bn is benzyl (i.e., CFhPh), RT is room temperature (and is 23°C unless otherwise indicated), CF ₃ SO ₃ - is triflate, and cyHx is cyclohexyl.

[0065] The term “naphthyl” or “naphthyl group” refers to an aromatic residue including a general formula C10H7. Generally, naphthyl or naphthyl groups are derived from a naphthalene having two fused benzene rings.

[0066] "Optional" or ''optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. For example, the phrase "optionally substituted hydrocarbyl" means that a hydrocarbyl moiety may or may not be substituted and that the description includes both unsubstituted hydrocarbyl and hydrocarbyl where there is substitution.

[0067] The term “oxadiazole” refers to an aromatic heterocycle that includes the general formula C2H2N2O. Oxadiazoles have four isomers.

[0068] A "polymer" has two or more of the same or different mer units. A "homopolymer" is a polymer having mer units that are the same. A "copolymer" is a polymer having two or more mer units that are different from each other. For the purpose of this disclosure, a copolymer does not include graft copolymers.

[0069] A "terpolymer" is a polymer having three mer units that are different from each other. A "tetrapolymer" is a polymer having four mer units that are different from each other. Accordingly, the definition of copolymer, as used herein, includes terpolymers, tetrapolymers and the like. "Different" as used to refer to mer units indicates that the mer units differ from each other by at least one atom or are different isomerically.

[0070] The term “pyridine” refers to an aromatic heterocycle compound that includes the general formula of C5H5N.

[0071] The term “quinoline” refers to an aromatic heterocycle compound that includes the general formula C9H7N. A quinoline compound includes a fused benzene and pyridine rings connected by the C2 and C3 of pyridine.

[0072] The term "ring atom" means an atom that is part of a cyclic ring structure. By this definition, a benzyl group has six ring atoms and tetrahydrofuran has 5 ring atoms.

[0073] A "ring carbon atom" is a carbon atom that is part of a cyclic ring structure. By this definition, a benzyl group has six ring carbon atoms and para-methylstyrene also has six ring carbon atoms.

[0074] The term "saturated" refers to the lack of double and triple bonds between atoms of a radical group such as ethyl, cyclohexyl, pyrrolidinyl, and the like. The term "unsaturated" refers to the presence of one or more double and triple bonds between atoms of a radical group such as vinyl, allyl, acetylide, oxazolinyl, cyclohexenyl, acetyl and the like, and specifically includes alkenyl and alkynyl groups, as well as groups in which double bonds are delocalized, as in aryl and heteroaryl groups as defined below.

[0075] The term "substituted" as in "substituted hydrocarbyl," "substituted aryl," "substituted alkyl," and the like, means that in the group in question the hydrocarbyl, alkyl, aryl or other moiety that follows the term), at least one hydrogen atom bound to a carbon atom is replaced with one or more substituent groups such as hydroxy, alkoxy, alkylthio, phosphine, amino, halo, silyl, and the like. When the term "substituted" introduces a list of possible substituted groups, it is intended that the term apply to every member of that group. That is. tiie phrase "substituted alkyl, alkenyl and alkynyl" is to be interpreted as "substituted alkyl, substituted alkenyl and substituted alkynyl." Similarly, "optionally substituted alkyl, alkenyl and alkynyl" is to be interpreted as "optionally substituted alkyl, optionally substituted alkenyl and optionally substituted alkynyl."

[0076] For any particular compound disclosed herein, any general or specific structure presented also encompasses all conformational isomers, regio-isomers, and stereoisomers that may arise from a particular set of substituents, unless stated otherwise. Similarly, unless stated otherwise, the general or specific structure also encompasses all enantiomers, diastereomers, and other optical isomers whether in enantiomeric or racemic forms, as well as mixtures of stereoisomers, as would be recognized by a skilled artisan.

[0077] For purposes herein, suitable hydrocarbyl radicals independently selected from substituted or unsubstituted methyl, ethyl, ethenyl and isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, triacontyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicosenyl, heneicosenyl, docosenyl, tricosenyl, tetracosenyl, pentacosenyl, hexacosenyl, heptacosenyl, octacosenyl, nonacosenyl, triacontenyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, decynyl, undecynyl, dodecynyl, tridecynyl, tetradecynyl, pentadecynyl, hexadecynyl, heptadecynyl, octadecynyl, nonadecynyl, eicosynyl, heneicosynyl, docosynyl, tricosynyl, tetracosynyl, pentacosynyl, hexacosynyl, heptacosynyl, octacosynyl, nonacosynyl, and/or triacontynyl.

[0078] For purposes herein, suitable hydrocarbyl radicals may also include isomers of saturated, partially unsaturated and aromatic cyclic structures wherein the radical may additionally be subjected to the types of substitutions described above. The term "aryl", "aryl radical", and/or "aryl group" refers to aromatic cyclic structures, which may be substituted with hydrocarbyl radicals and/or functional groups as defined herein. Examples of aryl radicals include: acenaphthenyl, acenaphthylenyl, acridinyl, anthracenyl, benzanthracenyls, benzimidazolyl, benzisoxazolyl, benzofluoranthenyls, benzofiiranyl, benzoperylenyls, benzopyrenyls, benzothiazolyl, benzothiophenyls, benzoxazolyl, benzyl, carbazolyl, carbobnyl, chrysenyl, cinnolinyl, coronenyl, cyclohexyl, cyclohexenyl, methylcyclohexyl, dibenzoanthracenyls, fluoranthenyl, fluorenyl, furanyl, imidazolyl, indazolyl, indenopyrenyls, indolyl, indobnyl, isobenzofuranyl, isoindolyl, isoquinobnyl, isoxazolyl, methyl benzyl, methylphenyl, naphthyl, oxazolyl, phenanthrenyl, phenyl, purinyl, pyrazinyl, pyrazolyl, pyrenyl, pyridazinyl, pyridinyl, pyritnidinyl, pyrrolyl, quinazolinyl, quinolonyl, quinoxalinyl, thiazolyl, thiophenyl, and the like.

[0079] It is to be understood that for purposes herein, when a radical is listed, it indicates the base structure of the radical (the radical type) and unless explicitly stated otherwise, all other radicals formed when that radical is subjected to the substitutions defined above. Alkyl, alkenyl, and alkynyl radicals listed include all isomers including, where appropriate, cyclic isomers, for example, butyl includes n-butyl, 2-methylpropyl, 1 -methylpropyl, tert-butyl, and cyclobutyl (and analogous substituted cyclopropyls); pentyl includes n-pentyl, cyclopentyl,

1 -methylbutyl, 2-methylbutyl, 3-methylbutyl, 1 -ethylpropyl, and nevopentyl (and analogous substituted cyclobutyls and cyclopropyls); butenyl includes E and Z forms of 1-butenyl,

2-butenyl, 3-butenyl, 1 -methyl- 1 -propenyl, l-methyl-2-propenyl, 2-methyl-l -propenyl, and 2-methyl-2-propenyl (and cyclobutenyls and cyclopropenyls). Cyclic compounds having substitutions include all isomer forms, for example, methylphenyl would include orthomethylphenyl, meta-methylphenyl and para-methylphenyl; dimethylphenyl would include

2.3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-diphenyhnethyl,

3.4-dimethylphenyl, and 3,5-dimethylphenyl.

[0080] All numerical values within the detailed description herein are modified by “about” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

Ligands

[0081] As described herein, ligands useful connection with the present catalyst complexes include:

[0082] As used herein, ligands are sometimes referred to as “compounds” or in the singular as a “compound”.

[0083] In an embodiment, the ligand is a compound of the structural Formula I where R ¹ is independently selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl. In a compound of the structural Formula I, R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl, and R ² and R ³ may be joined to form a fused aromatic ring system. In an embodiment of the structural Formula I, R ¹ can be substituted alkyl or aryl, and R ² and R ³ can form a substituted naphthyl.

[0084] In an embodiment of a compound of the structural Formula I, R ¹ is selected from the group consisting of aryl and substituted aryl, and R ² , R ³ and R ⁴ are hydrogen.

[0085] Even more particularly, the compound of the structural Formula I is: [0086] In an embodiment, the present ligands can be a compound of the structural

Formula II: where n = 0, 1. In Formula II, R ¹ is independently selected from the group consisting of alkyl, substituted alkyl, and aryl. R ³ is independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl. R ⁵ is independently selected from the group consisting of pyridine, substituted pyridine, quinoline and substituted quinoline.

[0087] In an embodiment, the compound of structural Formula II, R ⁵ can be a substituted pyridine when n=0. In an embodiment, the compound of structural Formula II, R ⁵ is independently selected from the group consisting of substituted pyridine and substituted quinoline when n=l.

[0088] In an embodiment, the ligand of the present catalyst complex can be selected from the group consisting of: General Synthesis - Ligands

[0089] Provided below are general synthesis for making the ligands described herein.

[0090] Synthetic conditions for L4, L5, L7, L9 and L12: Substituted 2-hydroxybenzaldehyde (la) and homopiperazine (lb) were dissolved in methanol and stirred for 2 hours at ambient temperature. The product (lc) was collected via filtration.

[0091] Synthetic conditions for L6: 2-(tert-butyl)-4-methylphenol (2a), trimethylamine (TMA), magnesium chloride (MgCl ₂ ), and paraformaldehyde (2b) were dissolved in THF and stirred at 70°C for 2.5 hours. The intermediate 3-(tert-butyl)-2-hydroxy-5- methylbenzaldehyde (2c) and homopiperazine (2d) were then dissolved in methanol and stirred at ambient temperature overnight. The product (2e) was collected via filtration. [0092] Synthetic conditions for L8: 6-bromopicolinaldehyde (3 a), (2-((tetrahydro-2H- pyran-2-yl)oxy)-[l,l'-biphenyl]-3-yl)lithium (3b), zinc(II) chloride (ZnCh), and Pd(PtBu3)2 were dissolved in THF and stirred at 60°C overnight. The resulting intermediate (3c) and homopiperazine (3d) were dissolved in methanol and stirred at ambient temperature overnight. The product (3e) was collected via filtration.

[0093] Synthetic conditions for L9 and L13: The biaryldiol (4a), sodium hydride (NaH), and MOMC1 were stirred in THF for 2 hours. The protected intermediate (4b), tetramethylethylenediamine (TMEDA), n-Butyllithium (n-BuLi), dimethylformamide (DMF) were stirred in THF to obtain the crude product (4c). Following the hydrolysis of (4c) with concentrated HC1 in THF/MeOH, the intermediate (4d) and homopiperazine (4e) were dissolved in methanol and stirred at ambient temperature overnight. The product (4f) was collected via filtration. [0094] Synthetic conditions for LIO: 6-(2,5-dimethylphenyl) picolinaldehyde (5a),

3-amino-[l,l'-biphenyl]-2-ol (5b), and magnesium sulfate (MgSCh) were dissolved in methylene chloride and stirred overnight at ambient temperature to obtain the product (5c).

[0095] Synthetic conditions for Li l: 3-amino-[l,l'-biphenyl]-2-ol (6a) and 8-(2,5-dimethylphenyl)-4-(p-tolyl)quinoline-2-carbaldehyde (6b) were dissolved in ethanol and stirred at 60°C for 1 hour to obtain product (6c).

Catalyst Complex

[0096] The present catalyst complex is of the structural Formula III: where n = 0, 1 and R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl. In the structural Formula in, R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl. R ² and R ³ may be joined to form a fused aromatic ring system. R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline. M is Zn and Al. Each L is bis(trimethylsilyl)amine, methyl and ethyl. X is an integer between 1 and 3, and the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent.

[0097] In the catalyst complex of Formula in, when n=0, R ¹ can be a substituted aryl, R ² , R ³ and R ⁴ are each independently hydrogen, and R ⁵ is substituted imidazole.

[0098] The present catalyst compounds are useful in ring-opening polymerization of cyclic ethers and esters. In an embodiment, the method comprises the step of mixing a catalyst complex of the structural Formula III with one or more lactones to produce a plurality of polymers, wherein the plurality of polymers comprises one or more polyhydroxyalkanoates (PHA polymers). In an embodiment, the plurality of polymers is atactic and/or isotactic in varying ratios.

[0099] In an embodiment of the method of ring-opening polymerization of cyclic ethers and esters of Formula JU, the cyclic esters and esters are selected from the group of β-lactones, β-propiolactone and β-butyrolactone. In an embodiment, the method of ring-opening polymerization of cyclic ethers and esters include ring-opening polymerization of (R)-beta- butyrolactone and/or (S)-beta-butyrolactone, and/or copolymers of the same. In an embodiment of the method of ring-opening polymerization of cyclic ethers and esters of Formula III, the polymer is poly(hydroxylbutyrate) (PHB), a short chain PHA polymer.

[0100] As described in the example, the present methods of ring-opening polymerization may be carried out in situ. Further, in the present polymerization methods, the method includes using the catalyst complex of Formula HI. Moreover, polymerization using the present methods may be conducted at room temperature, above room temperature and up to 120°C, preferably between room temperature and 85°C.

[0101] Once the desired ligand is formed, it can be combined with a metal atom, ion, compound or other metal precursor compound, and in some embodiments the present compounds include any of the above-mentioned ligands in combination with an appropriate metal precursor and an optional activator. Once the catalyst complex is formed, the catalyst complex does not have to the initiator because an alcohol can be added to generate an alkyloxy initiator.

[0102] As noted above, the present catalyst complexes include combination of ligand and metal atom, ion, or compound, or metal precursor. Ligands can be combined with a metal compound or method precursor and the product of such combination is not determined if a product forms. For example, the ligand is added to a reaction vessel at the same time as the metal or metal precursor compound along with lactone, reactants, activators, scavengers, etc. Additionally, the ligand can be modified prior to addition to or after the addition of the metal precursor, e.g., through a deprotonation reaction or some other modification.

[0103] In general, the metal precursor can be characterized by the general formula M(L) _m where M is a metal selected from the group consisting of groups 2, 3, 12 and 13 and m is 1, 2, 3, 4. 5. or 6. Thus in various embodiments M can be selected from 12 and 13, preferably 12. Each L is a ligand independently selected from the group consisting of hydrogen, halogen, optionally substituted alkyl, heteroalkyl, allyl, diene, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, alkoxy, aryloxy, boryl, silyl, amino, phosphino, ether, thioether, phosphine, amine, carboxylate, alkylthio, arylthio, 1.3-dionate, oxalate, carbonate, nitrate, sulphate, and combinations thereof. Optionally, two or more L groups are joined into a ring structure. One or more of the ligands L may be ionically bonded to the metal M and, for example, L may be a non-coordinated or loosely coordinated or weakly coordinated anion (e.g., L may be selected from the group consisting of those anions described below in the conjunction with the activators). (See Marks et al., Chem. Rev. 2000, v.100, pp. 1391-1434, for a detailed discussion of these weak interactions.) The metal precursors may be monomeric, dimeric or higher orders thereof. Metal precursors include a metal selected from Zn and/ or Al.

[0104] Specific examples of suitable zinc and aluminum precursors include, but are not limited to zinc compounds such as dimethyl zinc, diethyl zinc, dibutyl zinc, diphenyl zinc, dibenzyl zinc etc. or alkoxy or amide complexes of zinc such as Zn(OPh)2, Zn(OPr)2, zinc bis[bis(trimethylsilylamide], Bis(2,2,6,6-tetramethylpiperidinyl)zinc etc. Specific examples of suitable aluminum precursors include, but are not limited to AlMe ₃ , AlEt ₃ , AlBu ³ , Al(isobutyl) ₃ Al(OPh) ₃ , Al(OBu) ₃ , etc.

[0105] The ligand to metal precursor compound ratio is typically in the range of about 0.01:1 to about 100:1 , about 0.1:1 to about 10:1 and about 1 :1, 2:1 or 3:1. An activator (also sometimes referred to as a “co-catalyst”) can also be used in the polymerization methods described herein. The activator “activates” the catalyst complex by converting the neutral catalyst compound to a catalytically active catalyst complex. Such activators can include trialkyl aluminum compounds: trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminu and alumoxanes including methyl alumoxane (MAO), modified methylalumoxane (MMAO), ethylalumoxane, isobutylalumoxane, and solid polymethylaluminoxane.

[0106] Non-coordinating anions (NCA) can also be the activator in the methods described herein including, for example, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, tris(pentafluorophenyl)boron, tri(n-butyl) ammonium tetrakis(pentafluorophenyl)borate, a tris perfluorophenyl boron metalloid precursor or a tris perfluoronaphthyl boron metalloid precursor, polyhalogenated heteroborane anions, boric acid, or combination thereof.

Synthesis In Situ Polymerization

[0107] As described herein, an in situ polymerization process was performed in a sealed nitrogen purged glovebox using an array of eight (8) reaction cells purged with nitrogen. Ligands and metal precursors (L) were placed in vials and dissolved in a first solvent solution to provide a catalyst solution. Each of the individual reaction cells were then injected with a second solvent solution comprising lactone and heated to a target temperature after which stirring commences.

[0108] For in situ catalyst generation, the metal precursor was added in solvent solution comprising toluene or similar solvent. The mixture was vortexed at room temperature for several minutes. If required by the experiment, an alcohol was added as a solution in a suitable solvent. The catalyst solution was injected sequentially into each of the reactor cells. Each injection was preceded by 200 microliters of buffer solvent and chased by an additional 1 mL of solvent. The needle was washed thoroughly with isohexane after each injection. Two (2) hours after the last catalyst injection, the cells were cooled to between 60°C and 70°C, and then removed from the glovebox for analysis. Aliquots were taken to obtain conversion and the polymer isolated as described in the below in the examples.

[0109] Table 1A and Table IB immediately below provide the details of each experiment where the amount of BnOH was 0.035 M and the reaction temperature was at 80°C. Each of the experiments was carried out for least for 2 hours.

Table 1A

Experiment Details Table 1A - (Cont.)

Experiment Details

Table IB

Experiment Details - continued [0110] The following non-limiting examples are provided to illustrate the disclosure.

EXAMPLES

Example 1

3-(l ,5-diazabicyclo[3.2.1 ]octan-8-yl)-2',5,5'-trimethyl-[l , l'-biphenyl]-2-ol (L4)

[0111] 2-hydroxy-2',5,5'-trimethyl-[l,r-biphenyl]-3-carbaldehyde (2.2 grams (“g”), 7.79 millimole (“mmol”) and homopiperazine (780 milligrams (“mg”), 7.79 mmol) were dissolved in 100 mL of methanol. A precipitate formed within 10 minutes (“min.”) The reaction was allowed to stir at ambient temperature for 2 hours (“h”), then filtered to collect the white solid product in 70% yield.

[0112] ¹ H NMR (500 MHz, CDCl ₃ , δ): 1.31 (s, 9H), 1.37 (m, 1H), 2.08 (m, 1H), 2.14 (s, 3H), 2.34 (s, 3H), 3.11 (m, 6H), 3.41 (m, 2H), 5.35 (app d, 1H), 7.07 (m, 3H), 7.16 (m, 1H), 7.50 (m, 1H); ¹³ C NMR (CDCl ₃ , δ): 19.6, 20.9, 21.7 (3C), 34.3, 49.5, 19.6, 54.1, 54.2, 88.5, 122.6 - 134.8 (12C).

Example 2

2-(l,5-diazabicyclo[3.2.1]octan-8-yl)-4,6-di-tert-butylph enol (Lδ)

[0113] 3,5 -di-tert-butyl-2-hydroxybenzaldehyde (2.0 g, 8.53 mmol) and homopiperazine

(940 mg, 9.38 mmol) were dissolved in 100 milliliters (“mL”) of methanol. A precipitate formed within 10 minutes. The reaction was allowed to stir at ambient temperature for 2 hours, then filtered to collect the white solid product in 58% yield.

[0114] ¹ H NMR (400 MHz, CDCI3, δ): 1.28 (s, 9H), 1.33 (m, 1H), 1.42 (s, 9H), 2.00 (m, 1H), 3.03 (m, 6H), 3.34 (m, 2H), 5.15 (s, 1H), 7.20 (s, 1H), 7.26 (m, 1H); ¹³ C NMR(CDCl ₃ , δ): 18.5, 29.6 (3C), 31.7 (3C), 34.2 (2C), 34.9 (2C), 49.6, 54.5, 88.4, 120.2, 121.3, 123.4, 135.5, 140.0, 154.2. Example 3

2-(l ,5-diazabicyclo[3.2.1 ]octan-8-yl)-6-(tert-butyl)-4-methylphenol (L6)

[0115] 2-(tert-butyl)-4-methylphenol (7.5 g, 45.6 mmol), trimethylamine (12.7 mL, 91.3 mmol), and magnesium chloride (6.5 g, 68.5 mmol) were dissolved in 300 mL of THF and stirred at ambient temperature for 20 minutes. Paraformaldehyde (6.8 g, 228.3 mmol) was added and the reaction heated at 70°C for 2.5 hours. The bright yellow mixture was quenched with 10% HC1 and extracted twice with ether. The combined organic portions were washed with brine, dried over MgSO4, filtered and concentrated to a pale yellow oil which became solid after standing. The product was obtained in 85% yield.

[0116] ¹ HNMR (500 MHz, CDCl ₃ , δ): 1.45 (s, 9H), 2.35 (s, 3H), 7.19 (s, lH), 7.36 (s, 1H), 9.83 (s, 1H), 11.65 (s, 1H); ¹³ C NMR (CDCI3, δ): 20.5, 29.7 (3C), 34.7, 120.4, 128.1, 131.4, 135.4, 138.0, 159.2, 197.0.

[0117] 3-(tert-butyl)-2-hydroxy-5-methylbenzaldehyde (5.0 g, 26.0 mmol) and homopiperzaine (2.86 g, 28.6 mmol) were dissolved in 200 mL of methanol and stirred at ambient temperature overnight. The white precipitate was collected by filtration and washed with pentane to give the product in 63% yield.

[0118] ¹ H NMR (500 MHz, CDCI3, δ): 1.39 (s, 10H), 2.25 (m, 1H), 2.24 (s, 3H), 3.02 (m, 6H), 3.43 (m, 2H), 5.23 (br s, 1H), 7.00 (s, 1H), 7.13 (s, 1H); ¹³ C NMR (CDCI3, δ): 18.5, 20.8, 29.5 (3C), 34.6, 50.0 (2C), 54.7 (2C), 88.2, 120.7, 124.8, 126.5, 127.2, 136.3, 154.3.

Example 4

2-(6-(l ,5-diazabicyclo[3.2. l]octan-8-yl)pyridin-2-yl)-4,6-di-tert-butylphenol (L7)

[0119] 6-(3,5-di-tert-butyl-2-hydroxyphenyl)picolinaldehyde (322 mg, 3.21 mmol) and homopiperazine (1.0 g, 3.21 mmol) were dissolved in 20 mL of methanol and stirred until starting material was consumed as monitored by TLC (about 1 hour). The solid was collected by filtration and recrystallized in ether to give the product as a pale yellow powder in 75% yield.

[0120] NMR (500 MHz, CDCb, δ): 1 .24 (m, 1 H), 1.36 (s, 9H), 1.52 (s, 9H), 2.00 (m, 1H), 2.80 (in, 2H), 3.04 (m, 2H), 3.15 (m, 2H), 3.43 (m, 2H), 5.16 (s. 1H), 7.40 (m, 1 H), 7.49 (in, 1H), 7.65 (m, 1H). 7.78 (m, 2H), 14.58 (br s, LIT).

Example 5

3-(6-(l ,5-diazabicyclo[3,2.1 ]octan-8-yi)pyridin-2-yl)-[1, 1'-biphenyl]-2-ol (L8) [0121] 6-(2-hydroxy-[1,l'-biphenyl]-3-y1)pico1inaldehyde: (2-((tetrahydro-2H-pyran-2- yi)oxy)-[ 1, l’-bipheny l]-3-yl)lithiani (1.0 g, 3.8 mmol) and zinc(II) chloride (0.57 g, 4.2 mmol) were combined in 2 ml., of toluene. Tetrahydrofuran (50 rnL) was added to form a clear solution. After stirring for 1 hour at ambient temperature, Pd (PtBu3)2 (40 mg, 0.07 mmol) and 6-bromopicoIinaldehyde (0.71 g, 3.8 mmol) were added and the reaction heated at 60°C overnight. Once cool, water was added and the mixture extracted with ethyl acetate. The organic layer was washed with brine, dried over MgSO ₄ , filtered and concentrated to a solid. The solid was washed with isohexane to give the product in 66% yield.

[0122] ¹ H NMR (500 MHz, CDCb, 3): 7.04 (in, HI), 7.43 (m, 4H), 7.66 (d, J - 8.0 Hz, 2H), 7.83 (d, J ~ 7.5 Hz, TH), 7.88 (m, 1H), 8.02 (m. 1 H), 8.18 (m, LIT), 10.06 (s, 1 H), 14.01 (br s, 1H); ^l3 C NMR (CDCb, 3): 1 18.3, 1 19.2, 1 19.9. 124.0, 126.1, 127.2 (2C), 128. 1 (2C), 129.5, 131.5, 133.4, 138.2, 138.9, 149.2, 156.9, 158.7, 190.9.

[0123] The above picolinaldehyde (0.50 g, 1.8 mrnoi) and homopiperazine (0.18 g, 1 ,8 mmol) were dissolved in 15 mb of methanol and stirred at ambient temperature overnight. The yellow precipitate was collected by filtration, dissolved in methylene chloride, filtered and the filtrate concentrated to give clean pyridyl diazepane product.

[0124] ¹ H NMR (500 MHz, CDCb, δ): 1.23 (m,lH), 1.97 (m, 1H), 2.75 (m, 2H), 3.01 (m, 2H), 3.12 (m, 2H), 3.40 (in, 2H), 6.98 (m, 1 H), 7.35 (m, 2H), 7.45 (m, 2H), 7.71 (m, 3H), 7.84 (111, 211), 14.92 (br s, 111). Example 6

Synthesis of 3,3'-di(l ,5-diazabicyclo[3.2.1]octan-8-yl)-[1 ,1-bipheny1]’2,2’-diol (L9) [0125] 2,2*-bis(methoxymethoxy)-1 ,1-biphenyl: Sodium hydride (1 .6 g, 69.8 mmol) was slowly added to a cold solution of [1 ,1-biphenyl]-2,2'-diol (5.0 g, 26.5 mmol) in 100 mL of THF. Upon the cessation of effervescence, MOMC1 (4.7 mL, 59.0 mmol) was added and the reaction warmed to ambient temperature over 2 hours. The mixture was poured onto ice, then extracted with ether. The ether portion was washed with brine, dried (MgSCL), filtered, and concentrated to a yellow oil, The protected biphenyl compound was obtained in 65% yield, Rf = 0.53 (30:70 acetonerisohexane).

[0126] ¹ H NMR (500 MHz, CDCh, δ): 3.35 (s, 6H), 5.08 (s, 4H), 7.09 (2H), 7.24 (m, 6H). [0127] 2.2'-dihydroxy-[l,r-biphenyl]-3,3’-dicarbaldehyde: The above protected biphenol (9,3 g, 34.0 mmol) and tetramethylethylenediamine (12.2 mL, 81.8 mmol) was dissolved in THF and cooled to - 40' ³ C. n-Buiyllithium (32.7 mL, 81.8 mmol) was added dropwise and the reaction stirred for 30 minutes at ambient temperature. It was then cooled to - 40°C as 12 mL of DMF were added. After warming to ambient, the reaction was quenched with saturated ammonium chloride. The mixture was extracted with ether, washed with brine, dried (MgSCL), filtered, and concentrated. The crude residue was dissolved in THF/MeOH and 1 mL of concentrated HC1 in 5 mL of methanol was added. The reaction was stirred at ambient temperature overnight, then quenched with water and extracted with ethyl acetate. The organic fraction was washed with brine, dried (MgSO ₄ , filtered, and concentrated. The product was obtained as a white solid in 30% yield over 2 steps.

[0128] ¹ H NMR (500 MHz, CDCI ₃ , 6): 7.22 (m, 2H), 7.68 (m. 411), 9,99 (s, 2H), 11.44 (s, 2H).

[0129] The above aldehyde ( 1 .2 g, 4.9 mmol ) and homopiperazine (0.99 g, 9.9 mmol) were dissolved in 15 mL of methanol and stirred at ambient temperature overnight. A solid was formed which was collected by filtration and washed with cold methanol to give the product as a soft pale yellow solid in. 20% yield. [0130] ¹ H NMR (500 MHz, CDCl ₃ , δ): 1.34 (m, 2H), 2.03 (tn, 2H), 2.98 (m, 12H), 3.38 (tn, 4H), 5.32 (s, 2H), 6.84 (t, J= 7.7 Hz, 2H), 7.22 (d, J= 7.0 Hz, 2H), 7.34 (d, J= 7.0 Hz, 2H); ¹³ C NMR (CDCI3, δ): 18.3 (2C), 49.7 (4C), 54.3 (4C), 88.2 (2C), 118.2 (2C), 120.5 (2C), 125.9 (2C), 126.8 (2C), 131.4 (2C), 155.1 (2C).

Example 7

3-((6-(2,5-dimethylphenyl)pyridin-2-yl)methylene)amino-[ 1 , 1 '-biphenyl]-2-ol (L 10)

[0131] 6-(2,5-dimethylphenyl)picolinaldehyde (388 mg, 1.8 mmol) and 3-amino-[l,l'- biphenyl]-2-ol (340 mg, 1.8 mmol) were dissolved in 10 mL of methylene chloride. Approximately 100 mg of MgSO ₄ was added and the reaction stirred overnight at ambient temperature, then filtered and concentrated. The residue was purified by silica gel column chromatography (30% acetone/isohexane) to give the product in 84% yield as a dark red oil. Rf = 0.37 (30:70 acetone:isohexane).

[0132] ¹ H NMR (500 MHz, CDCI3, δ): 2.37 (s, 3H), 2.39 (s, 3H), 7.01 (m, 1H), 7.47 (m, 9H), 7.68 (m, 2H), 7.90 (m, 1H), 8.19 (m, 1H), 8.99 (s, 1H).

Example 8 3-(((8-(2,5-dimethylphenyl)-4-(p-tolyl)quinolin-2-yl)methyle ne)amino)-[ 1 , 1 '-biphenyl]-2-ol

[0133] 8-(2,5-dimethylphenyl)-4-(p-tolyl)quinoline-2-carbaldehyde (0.5 g, 1.42 mmol) and 3-amino-[l,l'-biphenyl]-2-ol (264 mg, 1.42 mmol) were dissolved in 20 mL of ethanol. The mixture was heated to 60°C for 1 hour and an orange precipitate formed. The reaction was cooled to ambient temperature and the solid collected by filtration, giving the product in 67% yield. ¹ H NMR (400 MHz, CDCh, δ): 2.09 (s, 3H), 2.42 (s, 3H), 2.98 (s, 3H), 6.95 Cm, 111), 7.51 (m, 10H), 7.75 (s, 1H), 8.01 (m, 111), 8.23 (s, 111), 8.88 (s, 1H).

Example 9

[0135] Phenylphenol earboxaldehyde (5.0 g, 25.2 mmol) and homopiperazine (1.26 g, 12.6 mmol) were dissolved in methanol and stirred under ambient conditions for 45 minutes. Additional equivalents of homopiperazine were added until starting material was no longer present by TLC. The precipitate formed was isolated by filtration and recrystallized io give white crystals:

[0136] ¹ H NMR (500 MHz, CDCh, 6): 1.31 Cm, 1H), 2.01 (m, 1H), 3.00 (m, 6H), 3.37 (m, 211), 5.23 (s, 1.H), 6.85 (t, 7.5 Hz, 1 H), 7.31 (m, 5H), 7.59 (m , 2H), 12.98 (br s, Hl); ¹³ C NMR (125 MHz, CDCh, δ): 18.6, 50.0 (2C), 54.6 (2C), 88.4, 1 18.8, 121.4, 126.4, 126.8, 128.1 (2C), 129.4, 129.6 (2C), 130.7, 139.1 , 155.1. Example 10

Synthesis of 3,3'-di(I,5-diazabicyclo|3.2.i]octan-8-yl)-[ 1 ,1-binaphthalene]-2,2'diol (13)

[0137] 2,2‘-bis(methoxymethoxy)-[ 1 , 1 ’-binaphthalene]: [1 ,1 '-binaphthalene]-2,2’-diol

(10.0 g, 34.9 mmol) was dissolved in 200 mL of THE and cooled to (PC. Sodium hydride (2.1 g, 90.8 mmol) was added in portions. After 5 minutes, MOMCi (5.8 mL, 76.8 mmol) was added and the reaction wanned to ambient temperature over 2 hours. The mixture was poured onto ice, then extracted with ether. The ether portion was washed with brine, dried (MgSO ₄ ), filtered, and concentrated to a yellow oil. The protected binaphthalene was obtained in 98% yield. [0138] NMR (500 MHz, CDCh, δ) : 3.15 (m, 3H), 4.99 (m. 1 H), 5.08 (m, 1H), 7.17

(m, 1H) , 7.22 (m, 1 H), 734 (m, 1H), 7.59 (m, 1H), 7.88 (m, 1 H), 7.96 (m, 1H).

[0139] 2,2’-dihydroxy-[1 ,1-binaphtha1ene]-3,3’-dicarbaldehyde: The above protected binapthol (13.8 g, 36.8 mmol) and tetramethylethylenediamine (13.2 mL, 88.4 mmol) was dissolved in 150 mL of THF and cooled to -40°C. n-Butyllithium (35.3 mL, 88.4 mmol) was added dropwise and the reaction stirred for 30 minutes at ambient temperature. It was then cooled to - 40°C as 14 mL of DMF were added. After warming to ambient, the reaction was quenched with saturated ammonium chloride. The mixture was extracted with ether, washed with brine, dried (MgSO ₄ ), filtered, and concentrated to a red oil. The product was obtained in 98% yield.

[0140] ¹ H NMR (500 MHz, CDCl ₃ , δ): 2.88 (s, 3H), 4.71 (m, 2H), 7.21 (m, 1H), 7.43 (m, 1H), 7.52 (m, 1H), 8.09 (m, 1H), 8.63 (m, 1H), 10.57 (m, 1H).

[0141] The crude dicarbaldehyde (8.3 g, 19.2 mmol) was dissolved in 100 mL of THF. A solution of 2 mL of concentrated HC1 in 10 mL of methanol was added and the reaction heated at 60°C overnight. Upon cooling, water and ether were added. The organic portion was washed with brine, dried over MgSO4, filtered and concentrated to a yellow solid.

[0142] *H NMR (500 MHz, CDCI3, δ): 7.21 (m, 2H), 7.41 (m, 4H), 8.00 (m, 2H), 8.35 (s, 2H), 10.20 (s, 2H), 10.58 (s, 2H).

[0143] The above dialdehyde (2.0 g, 5.8 mmol) was dissolved in 50 mL of warm ethanol. Homopiperazine (1.17 g, 11.68 mmol) was added and the reaction stirred at ambient temperature for 2 days. A solid was formed which was collected by filtration and washed with cold methanol to give the product as a white powder in 84% yield.

[0144] ¹ H NMR (500 MHz, CDCI3, δ): 1.34 (m, 2H), 2.04 (m, 2H), 3.09 (m, 12H), 3.41 (m, 4H), 5.45 (s, 2H), 7.15 (m, 6H), 7.49 (d, J= 8.0 Hz, 2H), 7.99 (s, 2H); ¹³ C NMR (125 MHz, CDCI3, δ): 18.2 (2C), 49.7 (2C), 50.1 (2C), 54.2 (2C), 54.6 (2C), 88.2 (2C), 117.2 (2C), 122.5 (2C), 123.0 (2C), 124.5 (2C), 126.1 (2C), 126.2 (2C), 127.9 (2C), 128.2 (2C), 134.3 (2C), 153.2 (2C).

Example 11

[0145] To a gram of methylcyclohexane solution of LI (10 mg), 1 gram of solution of Zn(N(TMS)2)2 (8.52 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then β-butyrolactone (1.90 g) was added next. The solution was left stirring at 70°C overnight. The gellike polymer was washed with 3 mL MeOH and dried under vacuum to obtain the polymer at quantitative yield. The polymer is atactic with Pr of 0.48 calculated by ¹³ C NMR.

[0146] To a 1 g methylcyclohexane solution of L2 (10 mg), 1 g solution of Zn(N(TMS)z)2 (8.79 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then β-butyrolactone (1.96 g) was added neat. The solution was left stirring at 70°C overnight. The gellike polymer was washed with 3 mL MeOH and dried under vacuum to obtain the polymer at quantitative yield. The polymer is atactic with Pr of 0.48 calculated by ¹³ C NMR.

[0147] To a 1 g methylcyclohexane solution of L3 (10 mg), 1 g solution of Zn(N(TMS)z)2 (7.61 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then β-butyrolactone (1.70 g) was added neat. The solution was left stirring at 70°C overnight. The gellike polymer was washed with 3 mL MeOH and dried under vacuum to obtain the polymer at 92% yield. The polymer is atactic with Pr of 0.47 calculated by ¹³ C NMR.

Example 14 AIMe ₃ precursor.

[0148] To a l g methylcyclohexane solution of LI (lO mg), 1 g solution ofAlMes (3.18 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then β-butyrolactone (1.90 g) was added neat. The solution was left stirring at 70°C and came to a complete stop after one hour. The gellike polymer was washed with 3 mL MeOH and dried under vacuum to obtain the polymer at 1.85 g yield. The polymer is atactic with Pr of 0.55 calculated by ¹³ C NMR.

Example 15 ε-Caprolactone Polymerization.

[0149] To a 1 g toluene solution of L3 (20 mg), 1 g solution of Zn(N(TMS)2)2 (15.2 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then caprolactone (2.25 g) was added neat. The solution was left stirring at 75°C, and the reaction came to a stop due to viscosity after 15 minutes. The swollen gel was taken into 30 mL DCM and precipitated with MeOH. Washed with hexanes and MeOH and dried under vacuum. 2.08 g polymer isolated.

Example 16 ε-Caprolactone Polymerization using AlMes.

[0150] To a 1 g toluene solution of LI (20 mg), 1 g solution of AlMes (3.18 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then caprolactone (2.52 g) was added neat. The solution was left stirring at 70°C, and the reaction came to a stop due to viscosity after 30 minutes. The polymer was isolated by precipitation of swollen gel with MeOH and hexanes. The solvent was decanted and the polymer was dried in a vacuum oven to constant weight (2.40 g).

Example 17 ε-Caprolactone Polymerization, using Benzyl Alcohol as Initiator.

[0151] To a 1 g toluene solution of LI (20 mg), 1 g solution of Zn(N(TMS)2)2 (17.04 mg) was added at room temperature followed by the addition of benzyl alcohol (4.77 mg). The solution was left stirring for 3 minutes. Then caprolactone (2.52 g) was added neat. The solution was left stirring at room temperature, and the reaction came to a stop due to viscosity after 45 minutes. The polymer was isolated by precipitation of swollen gel with MeOH and hexanes. The solvent was decanted and the polymer was dried under vacuum to constant weight (2.08 g).

Example 18 β-hexanolactone Polymerization.

[0152] To a 1 g toluene solution of LI (10 mg), 1 g solution of Zn(N(TMS)2)2 (8.52 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then P-hexanolactone (2.52 g) was added neat. The solution was left stirring at 70°C overnight. The polymer was isolated by precipitation of swollen gel with MeOH and hexanes. The solvent was decanted and the polymer was dried under vacuum to constant weight (1.98 g). Example 19 β-butyrolactone Polymerization, Diethyl Zinc as a Metal Precursor.

[0153] To a 1 g toluene solution of LI (20 mg), 1 g solution of ZnEti (5.45 mg) was added at room temperature. The solution was left stirring for 10 minutes. Then β-butyrolactone (2.52 g) was added neat. The solution was left stirring at 70°C overnight. The polymer was isolated by precipitation of swollen gel with MeOH and hexanes. The solvent was decanted and the polymer was dried under vacuum (1.65 g).

Example 20

[0154] L6 (10 mg) in 1 g toluene was added to Zn[N(TMS)2]2 (13.77 mg) at room temperature, -butyrolactone (1.54 g) was added neat and left 75°C. The solution was left stirring for 2 days and completely solidified. 2 mL iPrOH was added and the solution was decanted after agitating the polymer. The polymer was washed with MeOH and hexanes, and dried under vacuum to constant weight (1.24 g).

Example 21

[0155] L4 (10 mg) in 1 g toluene was added to Zn[N(TMS)2]2 (10.59 mg) at room temperature. β-butyrolactone (1.18 g) was added neat and left 75°C. The solution was left stirring for 2 days and completely solidified. 2 mL iPrOH was added and the solution was decanted after agitating the polymer. The polymer was washed with MeOH and hexanes, and dried under vacuum to constant weight (0.98 g).

Example 22

[0156] L5 (10 mg) in 1 g toluene was added to Zn[N(TMS)2]2 (12.20 mg) at room temperature. β-butyrolactone (1.36 g) was added neat and left 75°C. The solution was left stirring for 2 days and completely solidified. 2 mL iPrOH was added and the solution was decanted after agitating the polymer. The polymer was washed with MeOH and hexanes, and dried under vacuum to constant weight (1.12 g).

Example 23

[0157] L12 (10 mg) in 1 g toluene was added to Zn[N(TMS)2]2 (14.07 mg) at room temperature, -butyrolactone (1.57 g) was added neat and left 75°C. The solution was left stirring for 2 days and completely solidified. 2 mL iPrOH was added and the solution was decanted after agitating the polymer. The polymer was washed with MeOH and hexanes, and dried under vacuum to constant weight (1.16 g).

[0158] Table 2 below provides selected GPC data for Examples 13 to 23 described above. Table 2

GPC Data for Examples 13 to 23

[0159] Typically, zinc catalysts produce amorphous PHB polymers with no Tm or Tc. Only at lower temperature can selectivity be introduced. See Macromolecules, v.29(l l), (1996); FIG. 1A and IB.

[0160] Another method to introduce crystallinity to a PHB polymer made from racemic β-butyrolactone is to use chiral ligands. Ebrahimi et. al. demonstrated this approach to have Tm up to 80°C. Ebrahimi et al., Highly Active Chiral Zinc Catalysts for Immortal Polymerization of 0-Butyrolactone Form Melt Processable Syndio-Rich Poly(hydroxybutyrate), Macromolecules 2015, v.49(23), pp. 8812-8824. As shown in Examples 24 and 25 below, we discovered metal ligand combinations that can result in very high Tm and Tc even when the reactions are carried out at elevated temperatures.

Example 24

[0161] To a 0.5 g toluene solution of L10 (10 mg), 0.5 g toluene solution of Zn[N(TMS)i]2 (10.20 mg) was added at room temperature. The solution instantly turned dark red. 5 minutes later, β-butyrolactone (1.71 g) was added and left at 75°C for 16 hours. The thick dark red gel was poured onto MeOH and the solvent and washings were decanted away. Polymer dried in a vacuum oven to constant weight (1.1 g). Pr was determined to be 0.46 by ¹³ C NMR.

Example 25

[0162] To a 0.5 g toluene solution of LI 1 (10 mg), 0.5 g toluene solution of Zn[N(TMS)2]2 (7.45 mg) was added at room temperature. The solution instantly turned dark red. 5 minutes later, β-butyrolactone (1.24 g) was added and left at 75°C for 16 hours. The thick dark red gel was poured onto MeOH and the solvent and washings were decanted away. Polymer dried in a vacuum oven to constant weight (0.96 g). Pr was determined to be 0.46 by ¹³ C NMR.

[0163] DSC data for Examples 24 and 25 are provided below in Table 3 and FIG. 2A and 2B.

Table 3

DSC Data for Examples 24 and 25

[0164] We demonstrated this behavior with a second ligand family (Examples 20 to 23 herein) as well as shown in Table 4 below.

Table 4

DSC Data for Examples 24 and 25 Among the polymers described in Table 4, Entry 1 shows no features in its DSC trace whereas Entries 2 to 4 show Tms and crystalline behavior. Methylene regions in ¹³ C NMR of these polymers show slight changes. FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D, respectively. Similarly, carbonyl regions in ¹³ C NMRs also have only slight, variations. FIG. 4A, FIG, 4B, FIG. 4C, and FIG. 4D, respectively. Further, the DSC traces show crystalline features and very high Tms compared to literature examples for achiral ligand/Zn catalyst that operate at room temperature. FIG. 5A, FIG. 5B, and FIG. 5C, respectively.

Example 26

Synthesis of Isotactic PHB from R-beta-butyrolactone

[0165] We demonstrated polymerization of (R)-beta -butyrolactone (ee% :94%) to obtain highly isotactic PHB polymer. To a 35 mg of Zn(N(TMS)2)2, 1 g toluene solution of the ligand was added at room temperature. The solution was stirred for three minutes. 1.1 7 g (R)-beta- butyrolactone was then added to the solution, and left stirring at 80°C for 6 hours, then left at room temperature for 12 hours. The solution was then quenched with excess isopropanol. The solids were washed with isopropanol and hexanes and dried under nitrogen atmosphere (770 mg solids isolated). Carbonyl region of the polymer clearly indicates the highly isotactic microstructure of the polymer (Pm ~ 0.93). FIG. 6 shows the carbonyl region of the isotactic PHB. The MW and Mn obtained from DRI indicate that the polymer has a MW of 54,887 and Mn of 9,129 kg/mol.

[0166] Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any tipper limit are contemplated.

Additional Embodiments

[0167] Embodiment I. A compound of structural Formula I wherein

R ¹ is independently selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl; and

R ² and R ³ may be joined to form a fused aromatic ring system.

[0168] Embodiment 2. The compound of Embodiment 1, wherein R ¹ is substituted alkyl or aryl, and R ² and R ³ form a substituted naphthyl.

[0169] Embodiment 3. The compound of Embodiment 1, wherein R ¹ is selected from the group consisting of aryl and substituted aryl, and R ² , R ³ and R ⁴ are hydrogen.

[0170] Embodiment 4. A compound of the structural formula:

[0171] Embodiment 5. A compound of structural Formula II: wherein n = 0, 1

R ¹ is independently selected from the group consisting of alkyl, substituted alkyl, and aryl;

R ³ is independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl; and

R ⁵ is independently selected from the group consisting of pyridine, substituted pyridine, quinoline and substituted quinoline.

[0172] Embodiment 6. The compound of structural Formula II of Embodiment 5, wherein n=0 and R ⁵ is l,5-diazabicyclo[3.2.1]octane.

[0173] Embodiment 7. The compound of structural Formula II of Embodiment 5, wherein n=l and R ⁵ is independently selected from the group consisting of substituted pyridine and substituted quinoline. [0174] Embodiment 8. A compound of the structural formula selected from the group consisting of:

[0175] Embodiment 9. A catalyst complex of FormulaIII: wherein n = 0, 1; R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl;

R ² and R ³ may be joined to form a fused aromatic ring system;

R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline;

M is Zn and Al; each L is bis(trimethylsilyl)amine, methyl and ethyl; x is an integer between 1 and 3; and the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent. [0176] Embodiment 10. The catalyst complex of Embodiment 9, wherein n=0, R ¹ is substituted aryl, R ² , R ³ and R ⁴ are each independently hydrogen, and R ⁵ is substituted imidazole.

[0177] Embodiment 11. A method of ring-opening polymerization of cyclic ethers and esters comprising the step of mixing a catalyst complex of the structural Formula HI with one or more lactones to produce a plurality of polymers, wherein the plurality of polymers comprises one or more PHA polymers and the structural Formula in is: wherein n = 0 and 1 ;

R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl;

R ² and R ³ may be joined to form a fused aromatic ring system; R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline;

M is Zn and Al; each L is bis(trimethylsilyl)amine, methyl and ethyl; x is an integer between 1 and 3; and the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent. [0178] Embodiment 12. The method of ring-opening polymerization of cyclic ethers and esters of Embodiment 11 , wherein the cyclic esters and esters are selected from the group of P-lactones, P-propiolactone and β-butyrolactone.

[0179] Embodiment 13. The method of ring-opening polymerization of cyclic ethers and esters of Embodiment 11 , wherein the polymer is poly(hydroxylbutyrate) (PHB).

[0180] Embodiment 14. A method of in situ ring-opening polymerization of β-butyrolactone comprising the steps of: dissolving one or more ligands and one or more metal precursors in a first solvent solution to produce a catalyst solution, wherein the catalyst solution comprises a catalyst complex of the structural Formula III: wherein n = 0 and 1 ;

R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl; and

R ² and R ³ may be joined to form a fused aromatic ring system.

R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline;

M is Zn and Al; each L is bis(trimethylsilyl)amine, methyl and ethyl; x is an integer between 1 and 3; and the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent; heating a second solvent solution comprising at least one lactone and a second solvent; and injecting the catalyst solution into the lactone solution to produce a polymer.

[0181] Embodiment 15. The method in situ ring-opening polymerization of β-butyro lactone of Embodiment 14, wherein the ligand is a compound selected from the group of Formula I or Formula IL

[0182] Embodiment 16. A method of making a polyhydroxyalkanoate (PHA) polymer by ring-opening polymerization comprising the step of polymerizing a lactone in the presence of a solvent and a catalyst complex of the structural Formula III: n = 0 and 1 ;

R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl; and

R ² and R ³ may be joined to form a fused aromatic ring system.

R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline;

M is Zn and Al; each L is bis(trimethylsilyl)amine, methyl and ethyl; x is an integer between 1 and 3; the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent; and the catalyst complex was formed in situ to produce one or more PHA polymers. [0183] Embodiment 17. In the polymerization of cyclic ethers and esters, an exemplary improvement comprises using catalyst of Formula III: wherein n = 0 and 1 ;

R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl; and

R ² and R ³ may be joined to form a fused aromatic ring system.

R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline;

M is Zn and Al; each L is bis(trimethylsilyl)amine, methyl and ethyl; x is an integer between 1 and 3; and the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent. [0184] Embodiment 18. A method for preparing polyhydroxyalkanoate (PHA) polymer comprising providing a cyclic ester having a ring size from 3 to 6 atoms and subjecting the cyclic esters to ring-opening copolymerization using as catalyst a compound of the structural Formula III: wherein n = 0 and 1 ; R ¹ , R ² , R ³ , R ⁴ are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, naphthyl and substituted naphthyl;

R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, alkyl, and substituted alkyl; and R ² and R ³ may be joined to form a fused aromatic ring system.

R ⁵ is independently selected from the group consisting of aryl, substituted aryl, imidazole, substituted imidazole, oxadiazole, substituted oxadiazole, pyridine, substituted pyridine, quinoline and substituted quinoline;

M is Zn and Al; each L is bis(trimethylsilyl)amine, methyl and ethyl; x is an integer between 1 and 3; and the bond between the heteroaromatic nitrogen (N) and the metal (M) is dative or absent, wherein PHA polymer and/or random or block copolymers are produced.

[0185] Embodiment 19. The method of Embodiment 18, wherein the lactone is selected from β-propiolactone and β-butyrolactone.

[0186] Embodiment 20. The method according to any of Embodiments 11, 14, 15, 16, 18 and 19, wherein polymerization takes place at a temperature above 20°C.