To investigate the nature of the M-H interactions in transition metal polyhydrides, we have determined the structure of the complex Cp*MoH3(dppe) by single crystal neutron diffraction using SXD. This complex reveals an unexpected geometry, with two H atoms being placed at a distance from each other that is too long for a direct H-H interaction (H2-H3 ~ 1.4 Å), but short compared to typical classical polyhydrides (~ 1.8 Å). Furthermore, one-electron oxidation of the metal induces a significant closing of the H-H separation. This the first structurally characterised example of two polyhydride complexes having the same composition but differing by one electron, illustrating the effect of the metal oxidation state on the tendency of polyhydrides to undergo collapse and elimination of H2.
M Baya, J Houghton, J-C Daran, R Poli (Laboratoire de Chimie de Coordination, France), L Male, A Albinati (Università di Milano, Italy), M Gutmann (ISIS)
Research date: December 2007
M Baya et al., Chem. Eur. J. 13 (2007) 5347