Understanding the readiness of silane dissociation in transition metal η2-silane complexes Cp(CO)2M[η2-H(SiH3-nCln)] (M = Mn, Tc, and Re; n=1-3)

The influence of electronegative substituents at silicon and the effect of metal centers on the silane dissociation energies of transition metal eta(2)-silane complexes, Cp(CO)(2)M[eta(2)-H(SiH3-nCLn)] (M = Mn, Tc, and Re; n = 1-3), were studied by ab initio and density functional theory calculations. The M-Si and Si ... H interactions in relation to the readiness of silane dissociation are also examined. The calculated dissociation. energies are found to increase down the group as a result of the more diffused orbitals for the third-series transition metal. The dissociation energies also increase with the number of the chloride substituents. With the increase of the chloride substituents, the M-Si interaction is significantly enhanced and is responsible for the increasing dissociation energies. The Si ... H distances do not decrease as a result of increasing M-Si interaction when the chloride substituents at silicon increase. These results are related to the tendency of the silicon center to be hypervalent.