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Synthesis and Reactivity of Rare Earth Metal Alkyl Complexes Stabilized by Anilido Phosphinimine and Amino Phosphine Ligands
Author(s) -
Liu Bo,
Cui Dongmei,
Ma Jia,
Chen Xuesi,
Jing Xiabin
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601125
Subject(s) - phosphine , alkyl , reactivity (psychology) , rare earth , chemistry , metal , polymer chemistry , organic chemistry , stereochemistry , catalysis , mineralogy , medicine , pathology , alternative medicine
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 CH 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 i Pr 2 ‐2,6) 2 ] ( 2 ) selectively, that is, the CH 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= i Pr; 4 d : Ln=Y, R= i Pr) 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 i Pr 2 ‐2,6) 2 (thf)] ( 5 a : R=Me; 5 b : R= i Pr). Complexes 1 a , b and 4 a–d initiated the ring‐opening polymerization of d,l ‐lactide with high activity to give atactic polylactides.