Transition metal silane complexes

Transition metal silane complexes are coordination compounds containing hydrosilane ligands. An early example is (MeC5H4)Mn(CO)2(η2-HSiPh3) (Ph = C6H5).[1]

Oxidative addition of hydrosilane, showing proposed intermediate.

The bonding in silane sigma complexes is similar to that invoked in agostic interactions. The metal center engages the Si-H entity via a 3-center, 2-electron bond. It is widely assumed that these sigma complexes are intermediates in the oxidative addition of hydrosilanes to give metal silyl hydrides. This transformation is invoked in hydrosilylation catalysis.

A sigma complex derived from (MeC5H4)Mn(CO)3 and triphenylsilane.

Evidence for sigma-silane complexes is provided by proton NMR spectroscopy. For (MeC5H4)Mn(CO)2(η2-HSiPh3), J(29Si,1H) = 65 Hz compared to 180 Hz in free diphenylsilane. In silyl hydride complexes, the coupling in about 6 Hz. Neutron diffraction studies reveal a Si-H distance of 1.802(5) Å in the corresponding η2-HSiFPh2 complex vs 1.48 Å in free HSiFPh2. Elongated Si-H bonds are characteristic of these sigma complexes.[2]

References
  1. Corey, Joyce Y. (2011). "Reactions of Hydrosilanes with Transition Metal Complexes and Characterization of the Products". Chemical Reviews. 111: 863–1071. doi:10.1021/cr900359c. PMID 21250634.
  2. Nikonov, G. I. (2005). "Recent Advances in Nonclassical Interligand SiH Interactions". Adv. Organomet. Chem. 53: 217-309. doi:10.1016/s0065-3055(05)53006-5.
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