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Syntheses and Structures of Tris‐β‐Diketiminate Lanthanide Complexes and Their High Activity for Ring‐Opening Polymerization of ϵ‐Caprolactone and L ‐Lactide
Author(s) -
Xue Mingqiang,
Jiao Rui,
Zhang Yong,
Yao Yingming,
Shen Qi
Publication year - 2009
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200900313
Subject(s) - chemistry , lanthanide , polymerization , tris , metathesis , anhydrous , medicinal chemistry , polymer chemistry , lactide , ring opening polymerization , coordination sphere , salt metathesis reaction , caprolactone , stereochemistry , crystal structure , polymer , crystallography , organic chemistry , ion , biochemistry
Metathesis of {[(4–XC 6 H 4 )NC(Me)] 2 CH}Li with anhydrous lanthanide trichlorides (LnCl 3 ) in a 3:1 molar ratio yielded a series of tris‐β‐diketiminate complexes with the general formula [LnL X 3 ] [X = Cl, L Cl : Ln = Pr ( 1 ), Nd ( 2 ), Sm ( 3 ); X = H, L: Ln = Nd ( 4 ); X = Me, L Me : Ln = Nd ( 5 )]. Reaction of sodium salt of β‐diketiminate with anhydrous LnCl 3 in a 1:1 molar ratio in thf afforded the corresponding β‐diketiminate lanthanide dichlorides [L Cl PrCl 2 (thf) 2 ] ( 6 ), [L Me NdCl 2 (thf) 2 ] ( 7 ), and [L i Pr 2NdCl 2 (thf) 2 ] {L i Pr 2= [(2,6‐ i Pr 2 C 6 H 3 )NC(Me)] 2 CH – } ( 8 ), respectively. Each of these complexes was characterized, and the molecular structures of complexes 1 – 5 and 8 were determined by X‐ray single‐crystal structure analysis. Complexes 1 – 5 were found to be very active single‐component initiators for the ring‐opening polymerization of ϵ‐caprolactone (ϵ‐CL) and L ‐lactide ( L ‐LA) under mild conditions, giving polymers with high molecular weight and moderate polydispersities, whereas complexes 6 – 8 displayed no activity under the same polymerization conditions. The high catalytic activity shown by tris‐β‐diketiminate lanthanide complexes may be attributed to the activated Ln–β‐diketiminate bond caused by the crowded coordination sphere around the central metal.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)