Gas-Phase Synthesis of the Elusive Trisilicontetrahydride Species (Si3H4).

Abstract

The bimolecular gas-phase reaction of ground-state atomic silicon (Si; 3P) with disilane (Si2H6; 1A1g) was explored under single-collision conditions in a crossed molecular beam machine at a collision energy of 21 kJ mol-1. Combined with electronic structure calculations, the results suggest the formation of Si3H4 isomer(s) along with molecular hydrogen via indirect scattering dynamics through Si3H6 collision complex(es) and intersystem crossing from the triplet to the singlet surface. The nonadiabatic reaction dynamics can synthesize the energetically accessible singlet Si3H4 isomers in overall exoergic reaction(s) (-93 ± 21 kJ mol-1). All reasonable reaction products are either cyclic or hydrogen-bridged suggesting extensive isomerization processes from the reactants via the initially formed collision complex(es) to the fragmenting singlet intermediate(s). The underlying chemical dynamics of the silicon-disilane reaction are quite distinct from the isovalent carbon-ethane system that does not depict any reactivity at all, and open the door for an unconventional gas phase synthesis of hitherto elusive organosilicon molecules under single-collision conditions.