| 17048289 |
Liu B, Cui D, Ma J, Chen X, Jing X: Synthesis and reactivity of rare earth metal alkyl complexes stabilized by anilido phosphinimine and amino phosphine ligands. Chemistry. 2007;13(3):834-45.
Anilido phosphinimino ancillary ligand H (2) L (1) reacted with one equivalent of rare earth metal trialkyl [Ln{CH (2) Si (CH (3))(3)}(3)(thf)(2)] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L (1) LnCH (2) Si (CH (3))(3)(THF)] (1 a: Ln=Y; 1 b: Ln=Lu). In this process, deprotonation of H (2) L (1) by one metal alkyl species was followed by intramolecular C--H activation of the phenyl group of the phosphine moiety to generate dianionic species L (1) with release of two equivalnts of tetramethylsilane. Ligand L (1) coordinates to Ln (3+) ions in a rare C,N,N tridentate mode. Complex l a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL (1)) LnY (NHC (6) H (3) iPr (2)-2,6)(2)] (2) selectively, that is, the C--H activation of the phenyl group is reversible. When 1 a was exposed to moisture, the hydrolyzed dimeric complex [{(HL (1)) Y (OH)}(2)](OH)(2) (3) was isolated. Treatment of [Ln{CH (2) Si (CH (3))(3)}(3)(thf)(2)] with amino phosphine ligands HL (2-R) gave stable rare earth metal bis-alkyl complexes [(L (2-R)) Ln{CH (2) Si (CH (3))(3)}(2)(thf)] (4 a: Ln=Y, R=Me; 4 b: Ln=Lu, R=Me; 4 c: Ln=Y, R=iPr; 4 d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4 a and 4 c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L (2-R)) Y (NHC (6) H (3) iPr (2)-2,6)(2)(thf)] (5 a: R=Me; 5 b: R=iPr). Complexes 1 a,b and 4 a-d initiated the ring-opening polymerization of d,l-lactide with high activity to give atactic polylactides. |
81(1,1,1,1) |