A Family of 1,1,3,3‐Tetraalkylguanidine (H‐TAG) Solvated Zinc Aryloxide Precatalysts for the Ring‐Opening Polymerization of rac‐Lactide

Reaction of [Zn(μ-TAG){N(SiMe3)2}]2 {TAG = N=C[N(CH2CH3)2N(CH3)2] (DEDMG), N=C{[NCH2CH2CH2CdH2(N–Cd)]N(CH2CH3)2} (DEPYRG) and N=C{[NCH2CH2CH2CH2CeH2(N–Ce)]N(CH2CH3)2} (DEPIPG)} with 2 equiv. of ethanol (EtOH) and 2 equiv. of HOAr {OAr = OC6H3(CMe3)-2-(CH3)-6 (BMP) or OC6H2[C(CH3)3]2-2,6-(CH3)-4 (4MeDBP)} results in dizinc alkoxides with the general formula [Zn(μ-OEt)(OAr)(H-TAG)]2 (1–3). Et2Zn was additionally treated with 2 equiv. of 1,1,3,3-tetramethylguanidine (H-TMG) and H-BMP or HOC6H3(C6H5)2-2,6 to yield [Zn(BMP)2(H-TMG)2] (4) and [Zn{OC6H3(C6H5)2-2,6}2(H-TMG)2] (5). Complexes 1, 2, 4, and 5 were characterized by single-crystal X-ray diffraction. Polymerization of rac-lactide with 1–5 and [Zn(μ-OMe)(4MeDBP)(H-TMG)]2 (6) were found to generate polylactide (PLA). The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FTIR spectroscopy, and 1H and 13C NMR spectroscopic studies.

[1]  S. Bunge,et al.  Synthesis, structure, and reactivity of low-coordinate 1,1,3,3-tetraethylguanidinate complexes. , 2009, Inorganic chemistry.

[2]  Paul G. Hayes,et al.  Complexes of Mg, Ca and Zn as homogeneous catalysts for lactide polymerization. , 2009, Dalton transactions.

[3]  S. Bunge,et al.  Structurally characterized 1,1,3,3-tetramethylguanidine solvated magnesium aryloxide complexes: [Mg(mu-OEt)(DBP)(H-TMG)]2, [Mg(mu-OBc)(DBP)(H-TMG)]2, [Mg(mu-TMBA)(DBP)(H-TMG)]2, [Mg(mu-DPP)(DBP)(H-TMG)]2, [Mg(BMP)2(H-TMG)2], [Mg(O-2,6-Ph2C6H3)2 (H-TMG)2]. , 2009, Inorganic chemistry.

[4]  Sonja Herres-Pawlis,et al.  Lactide polymerisation with air-stable and highly active zinc complexes with guanidine-pyridine hybrid ligands. , 2009, Chemistry.

[5]  B. Patrick,et al.  Unusually Stable Chiral Ethyl Zinc Complexes: Reactivity and Polymerization of Lactide , 2009 .

[6]  Charlotte K. Williams,et al.  Biocompatible Initiators for Lactide Polymerization , 2008 .

[7]  Sonja Herres-Pawlis,et al.  [Bis(guanidine)]zinc Complexes and Their Application in Lactide Polymerisation , 2007 .

[8]  S. Bunge,et al.  Synthesis and characterization of a series of zinc complexes stabilized by 1,1,3,3-tetraalkylguanidinate (TAG) ligands: [Zn(μ-TAG){N(SiMe3)2}]2 , 2007 .

[9]  S. Bunge,et al.  Synthesis, Structure, and Reactivity of Alkylzinc Complexes Stabilized with 1,1,3,3-Tetramethylguanidine , 2007 .

[10]  S. Bunge,et al.  Stable analogs of the uranyl ion containing 1,1,3,3-tetramethylguanidine. , 2007, Dalton transactions.

[11]  D. Powell,et al.  Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, tau4. , 2007, Dalton transactions.

[12]  Jincai Wu,et al.  Recent developments in main group metal complexes catalyzed/initiated polymerization of lactides and related cyclic esters , 2006 .

[13]  M. P. Coles,et al.  Application of neutral amidines and guanidines in coordination chemistry. , 2006, Dalton transactions.

[14]  Bor-Hunn Huang,et al.  Ring-opening polymerization of lactide initiated by magnesium and zinc alkoxides , 2005 .

[15]  Michel Vert,et al.  Aliphatic polyesters: great degradable polymers that cannot do everything. , 2005, Biomacromolecules.

[16]  Xuesi Chen,et al.  Stereoselective polymerization of rac‐lactide with a bulky aluminum/Schiff base complex , 2004 .

[17]  Tsukasa Matsuo,et al.  Aryloxide-based multidentate ligands for early transition metals and f-element metals , 2004 .

[18]  M. Hillmyer,et al.  Stereoelective polymerization of D,L-lactide using N-heterocyclic carbene based compounds. , 2004, Chemical communications.

[19]  M. Chisholm,et al.  New generation polymers: the role of metal alkoxides as catalysts in the production of polyoxygenates , 2004 .

[20]  Odile Dechy-Cabaret,et al.  Controlled ring-opening polymerization of lactide and glycolide. , 2004, Chemical reviews.

[21]  Laura E. Matzen,et al.  Precursor Structural Influences on the Final ZnO Nanoparticle Morphology from a Novel Family of Structurally Characterized Zinc Alkoxy Alkyl Precursors , 2004 .

[22]  P. Hitchcock,et al.  Zinc Guanidinate Complexes and Their Application in Ring‐Opening Polymerisation Catalysis , 2004 .

[23]  David J. Williams,et al.  Remarkable stereocontrol in the polymerization of racemic lactide using aluminum initiators supported by tetradentate aminophenoxide ligands. , 2004, Journal of the American Chemical Society.

[24]  J. Carpentier,et al.  Stereoselective ring-opening polymerization of racemic lactide using alkoxy-amino-bis(phenolate) group 3 metal complexes. , 2004, Chemical communications.

[25]  A. Duda,et al.  Stereocontrolled polymerization of racemic lactide with chiral initiator: combining stereoelection and chiral ligand-exchange mechanism. , 2004, Journal of the American Chemical Society.

[26]  Ann-Christine Albertsson,et al.  Recent developments in ring opening polymerization of lactones for biomedical applications. , 2003, Biomacromolecules.

[27]  Charlotte K. Williams,et al.  A highly active zinc catalyst for the controlled polymerization of lactide. , 2003, Journal of the American Chemical Society.

[28]  J. Feijen,et al.  [(salen)Al]-Mediated, controlled and stereoselective ring-opening polymerization of lactide in solution and without solvent: synthesis of highly isotactic polylactide stereocopolymers from racemic D,L-lactide. , 2002, Angewandte Chemie.

[29]  J. C. Yarbrough,et al.  Solution and solid-state structural studies of epoxide adducts of cadmium phenoxides. Chemistry relevant to epoxide activation for ring-opening reactions. , 2002, Journal of the American Chemical Society.

[30]  J. Gallucci,et al.  Three-coordinate zinc amide and phenoxide complexes supported by a bulky Schiff base ligand. , 2001, Inorganic chemistry.

[31]  David R. Moore,et al.  Polymerization of lactide with zinc and magnesium beta-diiminate complexes: stereocontrol and mechanism. , 2001, Journal of the American Chemical Society.

[32]  M. J. Scott,et al.  Synthesis, Characterization, and Reactivity of Multinuclear Zinc(II) Alkyl Derivatives of Linked Phenoxides , 2001 .

[33]  P. Gruber,et al.  Polylactic Acid Technology , 2000 .

[34]  S. Iyer,et al.  Molecular Design of Single-Site Metal Alkoxide Catalyst Precursors for Ring-Opening Polymerization Reactions Leading to Polyoxygenates. 1. Polylactide Formation by Achiral and Chiral Magnesium and Zinc Alkoxides, (η3-L)MOR, Where L = Trispyrazolyl- and Trisindazolylborate Ligands , 2000 .

[35]  M. Zimmer,et al.  Catalytic activity of a series of Zn(II) phenoxides for the copolymerization of epoxides and carbon dioxide , 1999 .

[36]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[37]  G. Luinstra,et al.  The Ethylsulfinate Ligand: A Highly Efficient Initiating Group for the Zinc β-Diiminate Catalyzed Copolymerization Reaction of CO2 and Epoxides , 2003 .

[38]  H. Kricheldorf,et al.  Polylactones: 23. Polymerization of racemic and mesod,l-lactide with various organotin catalysts—stereochemical aspects , 1992 .

[39]  G. Deacon,et al.  Organoamido- and Aryloxo-lanthanoids. IV. Synthesis and X-Ray Structures of Low-Coordinate [Yb(O-2,4,6-But3C6H2)3(thf)] and [Yb(O-2,4,6-But3C6H2)2(μ-OH)(thf)]2 (thf = Tetrahydrofuran) , 1992 .