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

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)(η²-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. The 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/ethylbenzene formation. This complex shows an unusual distorted planar tetracoordinate environment at the central carbon atom positioned between the three Zr centers. The reaction of complex 5 with 2-cyanopyridine and acetonitrile is characterized by a reduction of the substrates. The herein reported reactivity of complex 5 demonstrates the remarkable potential of well-established dinuclear zirconocenes to stabilize unusual bond situations, which were analyzed comprehensively using spectroscopic, structural, and computational methods.