Abstract
Alane complexes of some bivalent ytterbocenes, L 2YbAlH 3·NEt 3 (L=C 5Me 5 ( IV), 1-SiMe 3Ind ( V), 9-SiMe 3Flu ( VI)) were found to provide stereospecific polymerization of methyl methacrylate. The apparent activities of initiators IV– VI were estimated to be a few times greater than those of their monometallic analogues L 2Yb·THF ( I– III). The polymerization was shown to proceed via the formation of a catalytically active intermediate, L 2YbAlH 2[OC(OMe)C(Me)CH 2C(Me) 2(CO 2Me)] which was proposed to exist in various forms. At low temperatures the alane fragment did not disrupt the stereocontrol mechanism originating from the metallocene template. The catalysts IV– VI produced an atactic pMMA at 0°C.
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