Synthesis and Reactivity of Rare Earth Metal Alkyl Complexes Stabilized by Anilido Phosphinimine and Amino Phosphine Ligands
作者:Bo Liu; Dongmei Cui; Jia Ma; Xuesi Chen and Xiabin Jing
关键字:C-H activation, lanthanides, N ligands, N,P ligands, ring-opening polymerization

Anilido phosphinimino ancillary ligand H2L1 reacted with one equivalent of rare earth metal trialkyl [Ln{CH2Si(CH3)3}3(thf)2] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L1LnCH2Si(CH3)3(THF)] (1?a: Ln=Y; 1?b: Ln=Lu). In this process, deprotonation of H2L1 by one metal alkyl species was followed by intramolecular C[BOND]H activation of the phenyl group of the phosphine moiety to generate dianionic species L1 with release of two equivalnts of tetramethylsilane. Ligand L1 coordinates to Ln3+ 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 [(HL1)LnY(NHC6H3iPr2-2,6)2] (2) selectively, that is, the C[BOND]H activation of the phenyl group is reversible. When 1?a was exposed to moisture, the hydrolyzed dimeric complex [{(HL1)Y(OH)}2](OH)2 (3) was isolated. Treatment of [Ln{CH2Si(CH3)3}3(thf)2] with amino phosphine ligands HL2-R gave stable rare earth metal bis-alkyl complexes [(L2-R)Ln{CH2Si(CH3)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 [(L2-R)Y(NHC6H3iPr2-2,6)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.