DESIGNING CATIONIC ZINC AND MAGNESIUM CATALYSTS FOR COORDINATION–INSERTION POLYMERIZATION OF LACTIDE

REFERENCES

• (a) Gupta , A. P. ; Kumar , V. New emerging trends in synthetic biodegradable polymers-polylactide: A critique . Eur. Polym. J. 2007 , 43 , 4053 – 4074 ; (b) Auras , R. ; Harte , B. ; Selke , S. An overview of polylactides as packaging materials . Macromol. Biosci. 2004 , 4 , 835 – 864 ; (c) Bogaert , J.-C. ; Coszach , P. Poly(lactic Acids): A potential solution to plastic waste dilemma . Macromol. Symp. 2000 , 153 , 287 – 303 ; (d) Lunt , J. Large-scale production, properties and commercial applications of polylactic acid polymers . Polym. Degrad. Stab. 1998 , 59 , 145 – 152 .
   Web of Science ®Google Scholar
• Natureworks LLC official website. http://www.natureworksllc.com (accessed August 23, 2011) .
   Google Scholar
• For selected recent reviews see: (a) Stanford , M. J. ; Dove , A. P. Stereocontrolled ring-opening polymerisation of lactide. Chem. Soc. Rev. 2010, 39, 486–494; (b) Ajellal , N. ; Carpentier , J.-F. ; Guillaume , C. ; Guillaume , S. M. ; Helou , M. ; Poirier , V. ; Sarazin , Y. ; Trifonov , A. Metal-catalyzed immortal ring-opening polymerization of lactones, lactides and cyclic carbonates. Dalton Trans. 2010, 39, 8363–8376; (c) Sutar , A. K. ; Maharana , T. ; Dutta , S. ; Chen , C.-T. ; Lin , C.-C. Ring-opening polymerization by lithium catalysts: an overview. Chem. Soc. Rev. 2010, 39, 1724–1746; (d) Wheaton , C. A. ; Hayes , P. G. ; Ireland , B. J. Complexes of Mg, Ca and Zn as homogeneous catalysts for lactide polymerization. Dalton Trans. 2009, 4832–4846; (e) Kricheldorf , H. R. Syntheses of Biodegradable and Biocompatible Polymers by Means of Bismuth Catalysts. Chem. Rev. 2009, 109, 5579–5594; (f) Wu , J. ; Yu , T.-L. ; Chen , C.-T. ; Lin , C.-C. Recent developments in main group metal complexes catalyzed/initiated polymerization of lactides and related cyclic esters. Coord. Chem. Rev. 2006, 250, 602–626.
   PubMed Web of Science ®Google Scholar
• (a) Cheng , M. ; Attygalle , A. B. ; Lobkovsky , E. B. ; Coates , G. W. Single-Site Catalysts for Ring-Opening Polymerization: Synthesis of Heterotactic Poly(lactic acid) from rac-Lactide / J. Am. Chem. Soc. 1999 , 121 , 11583 – 11584 ; (b) Chamberlain , B. M. ; Cheng , M. ; Moore , D. R. ; Ovitt , T. M. ; Lobkovsky , E. B. ; Coates , G. W. Polymerization of lactide with zinc and magnesium β-diiminate complexes: Stereocontrol and mechanism/ . Am. Chem. Soc. 2001 , 123 , 3229 – 3238 .
   Web of Science ®Google Scholar
• (a) Chisholm , M. H. ; Eilerts , N. W. Single-site metal alkoxide catalysts for ring-opening polymerizations. Poly(dilactide) synthesis employing {HB(3-Butpz)3}Mg(OEt) . Chem. Commun. 1996 , 853 – 854 ; (b) Chisholm , M. H. ; Eilerts , N. W. ; Huffman , J. C. ; Iyer , S. S. ; Pacold , M. ; Phomphrai , K. 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, (eta3-L)MOR, where L ˭ trispyrazolyl- and trisindazolylborate ligands . J. Am. Chem. Soc. 2000 , 122 , 11845 – 11854 ; (c) Chisholm , M. H. ; Huffman , J. C. ; Phomphrai , K. Monomeric metal alkoxides and trialkyl siloxides: (BDI)Mg(OtBu)(THF) and (BDI)Zn(OSiPh3)(THF). Comments on single site catalysts for ring-opening polymerization of lactides . Dalton Trans. 2001 , 222 – 224 ; (d) Chisholm , M. H. ; Gallucci , J. ; Phomphrai , K. Lactide polymerization by well-defined calcium coordination complexes: comparisons with related magnesium and zinc chemistry . Chem. Commun. 2003 , 48 – 49 ; (e) Chisholm , M. H. ; Gallucci , J. C. ; Phomphrai , K. Well-defined calcium initiators for lactide polymerization . Inorg. Chem. 2004 , 43 , 6717 – 6725 .
   Web of Science ®Google Scholar
• (a) Spassky , N. ; Wisniewski , M. ; Pluta , C. ; LeBorgne , A. Highly stereoselective polymerization of rac-(D,L)-lactide with a chiral Schiff's base/aluminium alkoxide initiator . Macromol. Chem. Phys. 1996 , 197 , 2627 – 2637 ; (b) Jhurry , D. ; Bhaw-Luximon , A. ; Spassky , N. Synthesis of polylactides by new aluminium Schoff's base complexes . Macromol. Symp. 2001 , 175 , 67 – 79 .
   Web of Science ®Google Scholar
• (a) Zhong , Z. Y. ; Dijkstra , P. J. ; Feijen , J. (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. Angew. Chem. Int. Ed. 2002, 41, 4510–4513; (b) Zhong , Z. Y. ; Dijkstra , P. J. ; Feijen , J. Controlled and stereoselective polymerization of lactide: Kinetics, selectivity, and microstructures. J. Am. Chem. Soc. 2003, 125, 11291–11298.
   PubMed Web of Science ®Google Scholar
• For selected recent examples see: (a) Sánchez-Barba , L. F. ; Garcés , A. ; Fernandez-Baeza , J. ; Otero , A. ; Alonso-Moreno , C. ; Lara-Sánchez , A. ; Rodríguez , A. M. Stereoselective Production of Poly(rac-lactide) by ROP with Highly Efficient Bulky Heteroscorpionate Alkylmagnesium Initiators. Organometallics 2011, 30, 2775–2789; (b) Liang , L. C. ; Tsai , T. L. ; Li , C. W. ; Hsu , Y. L. ; Lee , T. Y. Synthesis, Structure, and Ring-Opening Polymerization Catalysis of Zinc Complexes Containing Amido Phosphinimine Ligands. Eur. J. Inorg. Chem. 2011, 2948–2957; (c) Poirier , V. ; Roisnel , T. ; Carpentier , J.-F. ; Sarazin , Y. Zinc and magnesium complexes supported by bulky multidentate amino-ether phenolate ligands: potent pre-catalysts for the immortal ring-opening polymerisation of cyclic esters. Dalton Trans. 2011, 40, 523–534; (d) Borner , J. ; Florke , U. ; Doring , A. ; Kuckling , D. ; Jones , M. D. ; Steiner , M. ; Breuning , M. ; Herres-Pawlis , S. Unexpected activity of novel 9-Oxabispidine zinc complexes in lactide polymerization. Inorg. Chem. Commun. 2010, 13, 369–371; (e) Darensbourg , D. J. ; Karroonnirun , O. Ring-Opening Polymerization of Lactides Catalyzed by Natural Amino-Acid Based Zinc Catalysts. Inorg. Chem. 2010, 49, 2360–2371; (f) Di Iulio , C. ; Jones , M. D. ; Mahon , M. F. ; Apperley , D. C. Zinc(II) Silsesquioxane Complexes and Their Application for the Ring-Opening Polymerization of rac-Lactide. Inorg. Chem. 2010, 49, 10232–10234; (g) Drouin , F. ; Oguadinma , P. O. ; Whitehorne , T. J. J. ; Prud'homme , R. E. ; Schaper , F. Lactide Polymerization with Chiral β-Diketiminate Zinc Complexes. Organometallics 2010, 29, 2139–2147; (h) Garcés , A. ; Sánchez-Barba , L. F. ; Alonso-Moreno , C. ; Fajardo , M. ; Fernández-Baeza , J. ; Otero , A. ; Lara-Sánchez , A. ; López-Solera , I. ; Maria Rodríguez , A. Hybrid Scorpionate/Cyclopentadienyl Magnesium and Zinc Complexes: Synthesis, Coordination Chemistry, and Ring-Opening Polymerization Studies on Cyclic Esters. Inorg. Chem. 2010, 49, 2859–2871; (i) Wang , L. Y. ; Ma , H. Y. Zinc complexes supported by multidentate aminophenolate ligands: synthesis, structure and catalysis in ring-opening polymerization of rac-lactide. Dalton Trans. 2010, 39, 7897–7910; (j) Xu , X. ; Chen , Y. F. ; Zou , G. ; Ma , Z. ; Li , G. Y. Magnesium, zinc, and calcium complexes based on tridentate nitrogen ligands: Syntheses, structures, and catalytic activities to the ring opening polymerization of rac-lactide/ J. Organomet. Chem. 2010, 695, 1155–1162; (k) Hung , W. C. ; Lin , C.-C. Preparation, Characterization, and Catalytic Studies of Magnesium Complexes Supported by NNO-Tridentate Schiff-Base Ligands. Inorg. Chem. 2009, 48, 728–734; (l) Jones , M. D. ; Davidson , M. G. ; Keir , C. G. ; Hughes , L. M. ; Mahon , M. F. ; Apperley , D. C. Zinc(II) Homogeneous and Heterogeneous Species and Their Application for the Ring-Opening Polymerisation of rac-Lactide. Eur. J. Inorg. Chem. 2009, 635–642; (m) Labourdette , G. ; Lee , D. J. ; Patrick , B. O. ; Ezhova , M. B. ; Mehrkhodavandi , P. Unusually Stable Chiral Ethyl Zinc Complexes: Reactivity and Polymerization of Lactide. Organometallics 2009, 28, 1309–1319; (n) Poirier , V. ; Roisnel , T. ; Carpentier , J.-F. ; Sarazin , Y. Versatile catalytic systems based on complexes of zinc, magnesium and calcium supported by a bulky bis(morpholinomethyl)phenoxy ligand for the large-scale immortal ring-opening polymerisation of cyclic esters. Dalton Trans. 2009, 9820–9827; (o) Wang , L. ; Ma , H. Highly Active Magnesium Initiators for Ring-Opening Polymerization of rac-Lactide. Macromolecules 2010, 43, 6535–6537.
   Web of Science ®Google Scholar
• For selected recent examples see: (a) Otero , A. ; Lara-Sánchez , A. ; Fernández-Baeza , J. ; Alonso-Moreno , C. ; Márquez-Segovia , I. ; Sánchez-Barba , L. F. ; Castro-Osma , J. A. ; Rodríguez , A. M. Heteroscorpionate rare-earth initiators for the controlled ring-opening polymerization of Cyclic Esters. Dalton Trans. 2011, 40, 4687–4696; (b) Buffet , J.-C. ; Okuda , J. Scandium alkyl and amide complexes containing a cyclen-derived (NNNN) macrocyclic ligand: synthesis, structure and ring-opening polymerization activity toward lactide monomers. Dalton Trans. 2011, 40, 7748–7754; (c) Bouyahyi , M. ; Ajellal , N. ; Kirillov , E. ; Thomas , C. M. ; Carpentier , J.-F. Exploring Electronic versus Steric Effects in Stereoselective Ring-Opening Polymerization of Lactide and β-Butyrolactone with Amino-alkoxy-bis(phenolate)-Yttrium Complexes. Chem. Eur. 2011, 17, 1872–1883; (d) Nie , K. ; Gu , X. ; Yao , Y. ; Zhang , Y. ; Shen , Q. Synthesis and characterization of amine bridged bis(phenolate)lanthanide aryloxides and their application in the polymerization of lactide. Dalton Trans. 2010, 39, 6832–6840; (e) Luo , Y. ; Li , W. ; Lin , D. ; Yao , Y. ; Zhang , Y. ; Shen , Q. Lanthanide Alkyl Complexes Supported by a Piperazidine-Bridged Bis(phenolato) Ligand: Synthesis, Structural Characterization, and Catalysis for the Polymerization of L-Lactide and rac-Lactide. Organometallics 2010, 29, 3507–3514; (f) Lu , M. ; Yao , Y. ; Zhang , Y. ; Shen , Q. Synthesis and characterization of anionic rare-earth metal amides stabilized by phenoxy-amido ligands and their catalytic behavior for the polymerization of lactide. Dalton Trans. 2010, 39, 9530–9537; (g) Grunova , E. ; Kirillov , E. ; Roisnel , T. ; Carpentier , J.-F. Group 3 metal complexes supported by tridentate pyridine- and thiophene-linked bis(naphtholate) ligands: synthesis, structure, and use in stereoselective ring-opening polymerization of racemic lactide and β-Butyrolactone. Dalton Trans. 2010, 39, 6739–6752; (h) Dyer , H. E. ; Huijser , S. ; Susperregui , N. ; Bonnet , F. ; Schwarz , A. D. ; Duchateau , R. ; Maron , L. ; Mountford , P. Ring-Opening Polymerization of rac-Lactide by Bis(phenolate)amine-Supported Samarium Borohydride Complexes: An Experimental and DFT Study. Organometallics 2010, 29, 3602–3621; (i) Buchard , A. ; Platel , R. H. ; Auffrant , A. ; Le Goff , X. F. ; Le Floch , P. ; Williams , C. K. Iminophosphorane Neodymium(III) Complexes As Efficient Initiators for Lactide Polymerization. Organometallics 2010, 29, 2892–2900; (j) Platel , R. H. ; White , A. J. P. ; Williams , C. K. Stereocontrolled lactide polymerisation determined by the nuclearity of the yttrium initiator. Chem. Commun. 2009, 4115–4117.
   PubMed Web of Science ®Google Scholar
• For selected recent examples see: (a) Otero , A. ; Lara-Sánchez , A. ; Fernández-Baeza , J. ; Alonso-Moreno , C. ; Castro-Osma , J. A. ; Márquez-Segovia , I. ; Sánchez-Barba , L. F. ; Rodríguez , A. M. ; Garcia-Martinez , J.C Neutral and Cationic Aluminum Complexes Supported by Acetamidate and Thioacetamidate Heteroscorpionate Ligands as Initiators for Ring-Opening Polymerization of Cyclic Esters . Organometallics 2011 , 30 , 1507 – 1522 ; (b) Blake , M. P. ; Schwarz , A. D. ; Mountford , P. Sulfonamide, Phenolate, and Directing Ligand-Free Indium Initiators for the Ring-Opening Polymerization of rac-Lactide . Organometallics 2011 , 30 , 1202 – 1214 ; (c) Schwarz , A. D. ; Chu , Z. ; Mountford , P. Sulfonamide-Supported Aluminum Catalysts for the Ring-Opening Polymerization of rac-Lactide . Organometallics 2010 , 29 , 1246 – 1260 ; (d) Pietrangelo , A. ; Knight , S. C. ; Gupta , A. K. ; Yao , L. J. ; Hillmyer , M. A. ; Tolman , W. B. Mechanistic Study of the Stereoselective Polymerization of D,L-Lactide Using Indium(III) Halides / J. Am. Chem. Soc. 2010 , 132 , 11649 – 11657 ; (e) Hu , M. ; Wang , M. ; Zhang , P. ; Wang , L. ; Zhu , F. ; Sun , L. Preparation and structure of an enantiomeric water-bridged dinuclear indium complex containing two homochiral N atoms and its performance as an initiator in polymerization of rac-lactide . Inorg. Chem. Commun. 2010 , 13 , 968 – 971 ; (f) Horeglad , P. ; Kruk , P. ; Pécaut , J. Heteroselective Polymerization of rac-Lactide in the Presence of Dialkylgallium Alkoxides: The Effect of Lewis Base on Polymerization Stereoselectivity . Organometallics 2010 , 29 , 3729 – 3734 ; (g) Darensbourg , D. J. ; Karroonnirun , O. Stereoselective Ring-Opening Polymerization of rac-Lactides Catalyzed by Chiral and Achiral Aluminum Half-Salen Complexes . Organometallics 2010 , 29 , 5627 – 5634 ; (h) Buffet , J.-C. ; Okuda , J. ; Arnold , P. L. Chiral Indium Alkoxide Complexes as Initiators for the Stereoselective Ring-Opening Polymerization of rac-Lactide . Inorg. Chem. 2010 , 49 , 419 – 426 ; (i) Bouyahyi , M. ; Roisnel , T. ; Carpentier , J.-F. Aluminum Complexes of Fluorinated β-Diketonate Ligands: Syntheses, Structures, Intramolecular Reduction, and Use in Ring-Opening Polymerization of Lactide . Organometallics 2010 , 29 , 491 – 500 ; (j) Nomura , N. ; Ishii , R. ; Akakura , M. ; Aoi , K. Stereoselective ring-opening polymerization of racemic lactide using aluminum-achiral ligand complexes: exploration of a chain-end control mechanism/ . J. Am. Chem. Soc. 2002 , 124 , 5938 – 5939 ; (k) Pietrangelo , A. ; Hillmyer , M. A. ; Tolman , W. B. Stereoselective and controlled polymerization of D,L-lactide using Indium(III) Trichloride . Chem. Commun. 2009 , 2736 – 2737 .
   Web of Science ®Google Scholar
• For selected recent examples see: (a) Chen , L. ; Jia , L. ; Cheng , F. ; Wang , L. ; Lin , C.-C. ; Wu , J. ; Tang , N. Synthesis, characterization of sodium and potassium complexes and the application in ring-opening polymerization of L-lactide. lnorg. Chem. Commun. 2011, 14, 26–30; (b) Calvo , B. ; Davidson , M. G. ; García-Vivó , D. Polyamine-Stabilized Sodium Aryloxides: Simple Initiators for the Ring-Opening Polymerization of rac-Lactide. lnorg. Chem. 2011, 50, 3589–3595; (c) Huang , Y. ; Tsai , Y.-H. ; Hung , W.-C. ; Lin , C.-S. ; Wang , W. ; Huang , J.-H. ; Dutta , S. ; Lin , C.-C. Synthesis and Structural Studies of Lithium and Sodium Complexes with OOO-Tridentate Bis(phenolate) Ligands: Effective Catalysts for the Ring-Opening Polymerization of L-Lactide. lnorg. Chem. 2010, 49, 9416–9425.
   Web of Science ®Google Scholar
• For selected recent examples see: (a) Stopper , A. ; Goldberg , I. ; Kol , M. Bis(aniline-phenolate) complexes of group 4 metals: coordination chemistry and lactide polymerization catalysis . lnorg. Chem. Commun. 2011 , 14 , 715 – 718 ; (b) Saha , T. K. ; Ramkumar , V. ; Chakraborty , D. Salen Complexes of Zirconium and Hafnium: Synthesis, Structural Characterization, Controlled Hydrolysis, and Solvent-Free Ring-Opening Polymerization of Cyclic Esters and Lactides . lnorg. Chem. 2011 , 50 , 2720 – 2722 ; (c) Hancock , S. L. ; Mahon , M. F. ; Jones , M. D. Crystallographic characterisation of Ti(IV) piperazine complexes and their exploitation for the ring opening polymerisation of rac-lactide . Dalton Trans. 2011 , 40 , 2033 – 2037 ; (d) Buffet , J.-C. ; Okuda , J. Group 4 metal initiators for the controlled stereoselective polymerization of lactide monomers . Chem. Commun. 2011 , 47 , 4796 – 4798 ; (e) Whitelaw , E. L. ; Jones , M. D. ; Mahon , M. F. Group 4 Salalen Complexes and Their Application for the Ring-Opening Polymerization of rac-Lactide . Inorg. Chem. 2010 , 49 , 7176 – 7181 ; (f) Sergeeva , E. ; Kopilov , J. ; Goldberg , I. ; Kol , M. Dithiodiolate Ligands: Group 4 Complexes and Application in Lactide Polymerization . Inorg. Chem. 2010 , 49 , 3977 – 3979 ; (g) Saha , T. K. ; Rajashekhar , B. ; Gowda , R. R. ; Ramkumar , V. ; Chakraborty , D. Bis(imino)phenoxide complexes of zirconium: synthesis, structural characterization and solvent-free ring-opening polymerization of cyclic esters and lactides . Dalton Trans. 2010 , 39 , 5091 – 5093 ; (h) Jones , M. D. ; Davidson , M. G. ; Kociok-Kohn , G. New titanium and zirconium initiators for the production of polylactide . Polyhedron 2010 , 29 , 697 – 700 ; (i) Hu , M. ; Wang , M. ; Zhu , H. ; Zhang , L. ; Zhang , H. ; Sun , L. Preparation and structures of enantiomeric dinuclear zirconium and hafnium complexes containing two homochiral N atoms, and their catalytic property for polymerization of rac-lactide . Dalton Trans. 2010 , 39 , 4440 – 4446 ; (j) Zelikoff , A. L. ; Kopilov , J. ; Goldberg , I. ; Coates , G. W. ; Kol , M. New facets of an old ligand: titanium and zirconium complexes of phenylenediamine bis(phenolate) in lactide polymerisation catalysis . Chem. Commun. 2009 , 6804 – 6806 .
   Web of Science ®Google Scholar
• For selected recent examples see: (a) Gorczynski , J. L. ; Chen , J. B. ; Fraser , C. L. Iron tris(dibenzoylmethane)-centered polylactide stars: Multiple roles for the metal complex in lactide ring-opening polymerization. J. Am. Chem. Soc. 2005, 127, 14956–14957; (b) O'Keefe , B. J. ; Breyfogle , L. E. ; Hillmyer , M. A. ; Tolman , W. B. Mechanistic comparison of cyclic ester polymerizations by novel iron(III)-alkoxide complexes: Single vs multiple site catalysis. J. Am. Chem. Soc. 2002, 124, 4384–4393; (c) Gibson , V. C. ; Marshall , E. L. ; Navarro-Llobet , D. ; White , A. J. P. ; Williams , D. J. A well-defined iron(II) alkoxide initiator for the controlled polymerisation of lactide. J. Chem. Soc.-Dalton Trans. 2002, 4321–4322.
   PubMed Web of Science ®Google Scholar
• (a) Chen , E. Y.-X. ; Marks , T. J. Cocatalysts for metal-catalyzed olefin polymerization: Activators, activation processes, and structure-activity relationships . Chem. Rev. 2000 , 100 , 1391 – 1434 ; (b) Brintzinger , H. H. ; Fischer , D. ; Mulhaupt , R. ; Rieger , B. ; Waymouth , R. M. Stereospecific olefin polymerization with chiral metallocene catalysts . Angew. Chem. Int. Ed. Engl. 1995 , 34 , 1143 – 1170 .
   PubMed Web of Science ®Google Scholar
• (a) Cushion , M. G. ; Mountford , P. Cationic and charge-neutral calcium tetrahydroborate complexes and their use in the controlled ring-opening polymerisation of rac-lactide . Chem. Commun. 2011 , 47 , 2276 – 2278 ; (b) Clark , L. ; Cushion , M. G. ; Dyer , H. E. ; Schwarz , A. D. ; Duchateau , R. ; Mountford , P. Dicationic and zwitterionic catalysts for the amine-initiated, immortal ring-opening polymerisation of rac-lactide: facile synthesis of amine-terminated, highly heterotactic PLA . Chem. Commun. 2010 , 46 , 273 – 275 .
   PubMed Web of Science ®Google Scholar
• (a) Sarazin , Y. ; Liu , B. ; Roisnel , T. ; Maron , L. ; Carpentier , J.-F. Discrete, Solvent-Free Alkaline-Earth Metal Cations: Metal ⋯ Fluorine Interactions and ROP Catalytic Activity . J. Am. Chem. Soc. 2011 , 133 , 9069 – 9087 ; (b) Sarazin , Y. ; Poirier , V. ; Roisnel , T. ; Carpentier , J.-F. Discrete, Base-Free, Cationic Alkaline-Earth Complexes - Access and Catalytic Activity in the Polymerization of Lactide . Eur. J. Inorg. Chem. 2010 , 3423 – 3428 .
   PubMed Web of Science ®Google Scholar
• Zhu , D. ; Budzelaar , P. H. M. A measure for sigma-donor and pi-acceptor properties of diiminepyridine-type ligands . Organometallics 2008 , 27 , 2699 – 2705 .
   Web of Science ®Google Scholar
• Wheaton , C. A. ; Ireland , B. J. ; Hayes , P. G. Activated Zinc Complexes Supported by a Neutral, Phosphinimine-Containing Ligand: Synthesis and Efficacy for the Polymerization of Lactide . Organometallics 2009 , 28 , 1282 – 1285 .
   Web of Science ®Google Scholar
• Meyer , J. ; Staudinger , H. Uber neue organische Phosphorverbindungen 111. Phosphinmethylenderivate und Phosphinimine . Helv. Chim. Acta 1919 , 2 , 635 – 646 .
   Google Scholar
• Haenel , M. W. ; Jakubik , D. ; Rothenberger , E. ; Schroth , G. Bidentate Phosphines of Heteroarenes: 4,6-Bis(diphenylphosphino)dibenzofuran and 4,6-Bis(diphenylphosphino)dibenzothiophene . Chem. Ber. 1991 , 124 , 1705 – 1710 .
   Google Scholar
• Pilyugina , T. S. ; Schrock , R. R. ; Hock , A. S. ; Müller , P. Synthesis of Molybdenum(VI) Monoimido Alkyl and Alkylidene Complexes . Organometallics 2005 , 24 , 1929 – 1937 .
   Web of Science ®Google Scholar
• Piers , W. ; Chivers , T. Pentafluorophenylboranes: from obscurity to applications . Chem. Soc. Rev. 1997 , 26 , 345 – 354 .
   Web of Science ®Google Scholar
• Wheaton , C. A. ; Ireland , B. J. ; Hayes , P. G. Synthesis and Structural Diversity of ZnCl2 and Zn(C6F5)2 Complexes of a Phosphinimine Ligand. Z. Anorg. Allg. Chem. 2011, 637, 2111–2119.
   Web of Science ®Google Scholar
• Lewiński , J. ; Dutkiewicz , M. ; Lesiuk , M. ; Śliwiński , W. ; Zelga , K. ; Justyniak , I. ; Lipkowski , J. Solid-State Conversion of the Solvated Dimer [{tBuZn(μ-OtBu)(thf)}2] into a Long Overlooked Trimeric [{tBuZnOtBu}3] Species . Angew. Chem. Int. Ed. 2010 , 49 , 8266 – 8269 .
   PubMed Web of Science ®Google Scholar
• Chisholm , M. ; Gallucci , J. ; Phomphrai , K. Coordination chemistry and reactivity of monomeric alkoxides and amides of magnesium and zinc supported by the diiminato ligand CH(CMeNC6H3-2,6-iPr2)2: A Comparative study . Inorg. Chem. 2002 , 41 , 2785 – 2794 .
   PubMed Web of Science ®Google Scholar
• (a) Hannant , M. ; Schormann , M. ; Hughes , D. ; Bochmann , M. Synthesis of cationic zinc complexes from protonated diazadienes and ZnR2 (R ˭ Et, N(SiMe3)2). The crystal structures of [PriDADH][H2N{B(C6F5)3}2], [{PriDADZn(μ-OH)}2][H2N{B(C6F5)3}2]2, and [Ph*DADZnN(SiMe3)2][H2N{B(C6F5)3}2] . Inorg. Chim. Acta 2005 , 358 , 1683 – 1691 ; (b) Hannant , M. D. ; Schormann , M. ; Bochmann , M. Synthesis and Catalytic Activity of Three-Coordinate Zinc Cations . J. Chem. Soc., Dalton Trans. 2002 , 4071 – 4073 .
   Web of Science ®Google Scholar
• Horton , A. D. Direct Observation of β-Methyl Elimination in Cationic Neopentyl Complexes: Ligand Effects on the Reversible Elimination of Isobutene . Organometallics 1996 , 15 , 2675 – 2677 .
   Web of Science ®Google Scholar
• Ireland , B. J. ; Wheaton , C. A. ; Hayes , P. G. Cationic Organomagnesium Complexes as Highly Active Initiators for the Ring-Opening Polymerization of ϵ-Caprolactone . Organometallics 2010 , 29 , 1079 – 1084 .
   Web of Science ®Google Scholar
• Wheaton , C. A. ; Hayes , P. G. Cationic organozinc complexes of a bis(phosphinimine) pincer ligand: synthesis, structural and polymerization studies . Dalton Trans. 2010 , 39 , 3861 – 3869 .
   PubMed Web of Science ®Google Scholar
• Sarazin , Y. ; Schormann , M. ; Bochmann , M. Novel Zinc and Magnesium Alkyl and Amido Cations for Ring-Opening Polymerization Reactions . Organometallics 2004 , 23 , 3296 – 3302 .
   Web of Science ®Google Scholar
• Wheaton , C. A. ; Hayes , P. G. Exploring the Versatility of a Bis(Phosphinimine) Pincer Ligand: Effect of Sterics on Structure and Lactide Polymerization Activity of Cationic Zinc Complexes . Catal. Sci. Technol . 2012 , 2 , 125 – 138 .
   Web of Science ®Google Scholar
• Bondi , A. Van der Waals Volumes + Radii . J. Phys. Chem. 1964 , 68 , 441 – 451 .
   Web of Science ®Google Scholar
• Chisholm , M. H. ; Patmore , N. J. ; Zhou , Z. Concerning the relative importance of enantiomorphic site vs. chain end control in the stereoselective polymerization of lactides: reactions of (R,R-salen)- and (S,S-salen)-aluminium alkoxides LAlOCH2R complexes (R˭CH3 and S-CHMeCl) . Chem. Commun. 2005 , 127 – 129 .
   PubMed Web of Science ®Google Scholar
• Wheaton , C. A. ; Hayes , P. G. Cationic zinc complexes: a new class of catalyst for living lactide polymerization at ambient temperature. Chem. Commun. 2010, 46, 8404–8406.
   PubMed Web of Science ®Google Scholar
• (a) Douglas , A. F. ; Patrick , B. O. ; Mehrkhodavandi , P. A highly active chiral indium catalyst for living lactide polymerization . Angew. Chem. Int. Ed. 2008 , 47 , 2290 – 2293 ; (b) Chisholm , M. H. ; Delbridge , E. E. A study of the ring-opening polymerization (ROP) of L-lactide by Ph2SnX2 precursors (X˭NMe2, OPri): The notable influence of initiator group . New J. Chem. 2003 , 27 , 1177 – 1183 .
   PubMed Web of Science ®Google Scholar
• Wheaton , C. A. ; Hayes , P. G. Electron Deficient Zinc Complexes: Enhanced Lactide Polymerization Activity Achieved Through Rational Ligand Design . J. Organomet. Chem. submitted .
   Web of Science ®Google Scholar
• (a) Zhang , L. ; Nederberg , F. ; Messman , J. M. ; Pratt , R. C. ; Hedrick , J. L. ; Wade , C. G. Organocatalytic stereoselective ring-opening polymerization of lactide with dimeric phosphazene bases . J. Am. Chem. Soc. 2007 , 129 , 12610 – 12611 ; (b) Byers , J. A. ; Bercaw , J. E. Kinetic resolution of racemic α -olefins with ansa-zirconocene polymerization catalysts: Enantiomorphic site vs. chain end control . Proc. Nat. Acad. Sci. 2006 , 103 , 15303 – 15308 .
   PubMed Web of Science ®Google Scholar
• Sun , H. ; Ritch , J. S. ; Hayes , P. G. Toward Stereoselective Lactide Polymerization Catalysts: Cationic Zinc Complexes Supported by a Chiral Phosphinimine Scaffold . Inorg. Chem. 2011 , 50 , 8063 – 8072 .
   PubMed Web of Science ®Google Scholar
• Imamoto , T. ; Oshiki , T. ; Onozawa , T. ; Kusumoto , T. ; Sato , K. Synthesis and reactions of phosphine-boranes: Synthesis of new bidentate ligands with homochiral phosphine centers via optically pure phosphine-boranes . J. Am. Chem. Soc. 1990 , 112 , 5244 – 5252 .
   Web of Science ®Google Scholar
• Sun , H. ; Ritch , J. S. ; Hayes , P. G. Ring-opening polymerisation of rac-lactide mediated by cationic zinc complexes featuring P-stereogenic bisphosphinimine ligands . Dalton Trans. In Press. DOI: 10.1039/C2DT11954D .
   Web of Science ®Google Scholar