Toward Stereoselective Lactide Polymerization Catalysts: Cationic Zinc Complexes Supported by a Chiral Phosphinimine Scaffold

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• 作者：Hongsui Sun ; Jamie S. Ritch ; Paul G. Hayes
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：September 5, 2011
• 年：2011
• 卷：50
• 期：17
• 页码：8063-8072
• 全文大小：947K
• 年卷期：v.50,no.17(September 5, 2011)
• ISSN：1520-510X

文摘

The P-stereogenic phosphinimine ligands (dbf)MePhP鈺怤Ar (7: Ar = Dipp; 8: Ar = Mes; dbf = dibenzofuran, Dipp = 2,6-diisopropylphenyl, Mes = 2,4,6-trimethylphenyl) were synthesized as racemates via reactions of the parent phosphines (rac)-(dbf)MePhP (6) with organoazides. The ligands 7 and 8 were protonated by Br酶nsted acids to afford the aminophosphonium borate salts [(7)-H][BAr<sub>4sub>] (9: Ar = C<sub>6sub>F<sub>5sub>; 11: Ar = Ph) and [(8)-H][BAr<sub>4sub>] (10: Ar = C<sub>6sub>F<sub>5sub>; 12: Ar = Ph). The protonated ligands 9 and 10 were active toward alkane elimination reactions with diethylzinc and ethyl-[methyl-(S)-lactate]zinc to give the heteroleptic complexes [{(dbf)MePhP鈺怤Ar}ZnR][B(C<sub>6sub>F<sub>5sub>)<sub>4sub>] (Ar = Dipp, 13: R = Et; 15: R = methyl-(S)-lactate; Ar = Mes, 14: R = Et; 16: R = methyl-(S)-lactate). By contrast, reaction of the tetraphenylborate derivative 11 with diethylzinc yielded a phenyl transfer product, [(dbf)MePhP鈺怤Dipp]ZnPh<sub>2sub> (17). Complex 15 was found to catalyze the ring-opening polymerization of rac-lactide.