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]
![](../I/m/ArrestedOAofSiH.png)
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.
![](../I/m/SigmaSilaneCmpx.svg.png)
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
- 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.
- 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.