Reactions of di- and poly-nuclear complexes 13. Synthesis, structure and fluxional behaviour of hydrido- and thiolato- or selenato-bridged complexes [Mo 2Cp 2(μ-H)(μ-ER)(CO) 4] (E  S, R  Me, tBu, Bz, or Ph; E  Se, R  Ph)

Abstract

Oxidative addition of thiols or selenoles across the Mo 2 centre of [Mo 2Cp 2(CO) 4] gives complexes with bridging thiolate or selenate and hydride ligands [Mo 2Cp 2(μ-H)(μ-ER)(CO) 4](E  S, R  Me ( 4), tBu ( 5), Bz ( 6), Ph ( 7); E  Se, R  Ph ( 8)). The complex 4 is also formed on reaction of [Mo 2Cp 2(μ-SMe) 2(CO) 4] with vanadocene [VCp 2] with the possible involvement of a thioaldehyde, hydride derivative of the vanadocene. Crystals of 4 are monoclinic, space group C2/ c, with a = 17.225 (1), b = 8.418 (1) c = 22.960 (2) A ̊ , β = 90.346 (5)°, R = 0.023 for 4213 observed reflections. In the solid state, molecules of 4 contain a planar Mo 2(μ-H)(μ-S) core and the Cp ligands are cis with respect to the MoMo bond, the two CpMo(CO) 2 unites being related by an approximate plane of symmetry which contains the bridging H and S donor atoms and which is normal to the MoMo bond. The fluxional nature of complexes 4–8 in solution is shown from variable-temperature 1H and 13C NMR spectra to arise from cis-trans isomerisation.