The Dinuclear Zirconocene Complex [(Cp2Zr)2(µ-Me)(µ-C2Ph)] as a Platform for Small Molecule Activation.

Abstract

The dinuclear title compound [(Cp2Zr)2(µ-Me)(µ-C2Ph)] 5 was prepared from a zirconocene alkynyl methyl complex and Rosenthal's zirconocene source [Cp2Zr(py)(h2-Me3SiC2SiMe3)] in a formal comproportionation reaction. This complex shows catalytic activity for the dehydrocoupling of amine boranes, with a dinuclear hydride-bridged alkynyl complex 6 being formed as a catalytically relevant species. The structure of this complex was confirmed for the first time by single-crystal X-ray analysis. Reaction of complex 5 with hydrogen results in hydrogenation of the alkynyl ligand, yielding a highly labile trinuclear hydride-bridged complex as a possible intermediate of zirconocene dihydride/ethyl benzene formation. This complex shows an unusual distorted planar tetracoordinate environment at the central carbon atom positioned between the three Zr centres. The reaction of complex 5 with 2-cyanopyridine and acetonitrile is characterised by a reduction of the substrates. The herein reported reactivity of complex 5 demonstrates the remarkable potential of well-established zirconocenes to stabilise unusual bond situations, which were analysed comprehensively using spectroscopic, structural, and computational methods.