M-S Multiple Bond in HMSH, H2MS, and HMS Molecules (M = B, Al, Ga): Matrix Infrared Spectra and Theoretical Calculations.

Reaction products of B, Al, and Ga atoms with H2S have been identified in solid argon using matrix isolation infrared absorption spectroscopy. The results show that the ground state B atom reaction with H2S gives the H2BS molecule while for the Al atom the HAlSH molecule forms first, which then further isomerizes to H2AlS upon >500 nm irradiation. The reaction of the Ga atom with H2S only takes place upon photolysis to produce HGaSH in the matrix. The assignments of the major modes for these products were confirmed by appropriate 10B, 11B, D2S, and H234S isotopic shifts and theoretical frequency calculations. Topological analysis of the electron density suggests that both HBSH and H2BS molecules possess covalent B-S bond with significant double bond character, while the M-S bond in the heavier group 13 homologues (Al, Ga) was characterized as a polar covalent strong interaction.