Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada.
Inorg Chem. 2011 Sep 5;50(17):8063-72. doi: 10.1021/ic201139b. Epub 2011 Jul 26.
The P-stereogenic phosphinimine ligands (dbf)MePhP═NAr (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 Brønsted acids to afford the aminophosphonium borate salts [(7)-H][BAr(4)] (9: Ar = C(6)F(5); 11: Ar = Ph) and [(8)-H][BAr(4)] (10: Ar = C(6)F(5); 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═NAr}ZnR][B(C(6)F(5))(4)] (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═NDipp]ZnPh(2) (17). Complex 15 was found to catalyze the ring-opening polymerization of rac-lactide.
手性膦亚胺配体 (dbf)MePhP═NAr（7：Ar = Dipp；8：Ar = Mes；dbf = 二苯并呋喃，Dipp = 2,6-二异丙基苯基，Mes = 2,4,6-三甲基苯基）作为外消旋体通过亲核取代反应由母体膦 (rac)-(dbf)MePhP（6）与有机叠氮化物合成。配体 7 和 8 被质子化，得到氨基磷翁硼酸盐盐 [(7)-H][BAr(4)]（9：Ar = C(6)F(5)；11：Ar = Ph）和 [(8)-H][BAr(4)]（10：Ar = C(6)F(5)；12：Ar = Ph）。质子化的配体 9 和 10 对二乙基锌和乙基-[甲基-(S)-乳酸]锌的烷烃消除反应具有活性，生成杂配位配合物 [{(dbf)MePhP═NAr}ZnR][B(C(6)F(5))(4)]（Ar = Dipp，13：R = Et；15：R = 甲基-(S)-乳酸酯；Ar = Mes，14：R = Et；16：R = 甲基-(S)-乳酸酯）。相比之下，四苯硼酸盐衍生物 11 与二乙基锌反应生成苯转移产物，[(dbf)MePhP═NDipp]ZnPh(2)（17）。发现配合物 15 可以催化 rac-丙交酯的开环聚合。
