Half-Sandwich Alkyl and Hydrido Complexes of Yttrium: Convenient Synthesis and Polymerization Catalysis of Polar Monomers

Direct preparation of alkyl half-sandwich complexes of the heavier rare earth elements (such as 1) is possible by alkane elimination from the corresponding cyclopentadiene derivative and the trialkyl complex [Y(CH2SiMe3)3(thf)2]. Hydrogenation of 1 gives the highly fluxional dimeric hydride complex 2. Both complexes catalyze the polymerization of the polar monomers tert-butyl acrylate and acrylonitrile.