Synthesis and characterization of samarium bis(phenolate) complexes and their catalytic activity for the polymerization of L-lactide

The synthesis, structure and catalytic activity for the polymerization of L-lactide of samarium complexes supported by the carbon-bridged bis(phenolate) ligand 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP2-) are described. The reaction of (C5H5)(3)Sm(THF) with MBMPH2 in a 1:1 M ratio in THF at 50 degrees C produced the bis(phenolato) samarium complex (C5H5)Sm(MBMP)(THF)(2) (1) in a nearly quantitative yield. Complex 1 is a useful precursor for synthesizing bis(phenolato) samarium aryloxides. Complex 1 reacted with MBMPH2 in toluene at 80 degrees C to give the complex (MBMP)Sm(MBMPH)(THF)(2) (2). The reactions of complex 1 with some mono-phenols, including 2,6-di-tert-butyl-4-methylphenol, 2,6-diisopropylphenol, 2,6-dimethylphenol and 4-methoxyphenol, in toluene produce the complexes (MBMP)Sm(OC6H2-Bu-2(t)-2,6-Me-4)(THF)(2)(3), (MBMP)Sm(OC6H3-Pr-2(i)-2,6)(THF)(3) (4), (MBMP)Sm(OC6H3-Me-2-2,6)(DME)(2) (5) and [(MBMP)Sm(OC6H4-OMe-4)(THF)(2)](2) (6). All of these complexes were well characterized by elemental analyses, IR spectra and single-crystal X-ray structure determination, except for complex 2. It was found that complexes 3-6 are efficient initiators for L-lactide polymerization. (C) 2013 Elsevier Ltd. All rights reserved.