Double and Triple Si-H-M Bridge Bonds: Matrix Infrared Spectra and Theoretical Calculations for Reaction Products of Silane with Ti, Zr, and Hf Atoms.

Infrared spectra of matrix isolated dibridged Si(μ-H)2MH2 and tribridged Si(μ-H)3MH molecules (M = Zr and Hf) were observed following the laser-ablated metal atom reactions with SiH4 during condensation in excess argon and neon, but only the latter species was observed with titanium. Assignments of the major vibrational modes, which included terminal MH, MH2 and hydrogen bridge Si-H-M stretching modes, were confirmed by the appropriate SiD4 isotopic shifts and density functional vibrational frequency calculations (B3LYP and BPW91). The Si-H-M hydrogen bridge bond is calculated as weak covalent interaction and compared with the C-H···M agostic interaction in terms of electron localization function (ELF) analysis and noncovalent interaction index (NCI) calculations. Furthermore, the different products of Ti, Zr, and Hf reactions with SiH4 are discussed in detail.