Combined Crossed Molecular Beams and Ab Initio Study of the Bimolecular Reaction of Ground State Atomic Silicon (Si; 3P) with Germane (GeH4; X1A1).

The chemical dynamics of the elementary reaction of ground state atomic silicon (Si; 3 P) with germane (GeH 4 ; X 1 A 1 ) were unraveled in the gas phase under single collision condition at a collision energy of 11.8 ± 0.3 kJ mol -1 exploiting the crossed molecular beams technique contemplated with electronic structure calcu-la-tions. The reaction follows indirect scattering dynamics and is initiated through an initial barrierless insertion of the silicon atom into one of the four chemi-cally equivalent germanium-hydrogen bonds forming a triplet collision complex (HSiGeH 3 ; 3 i1 ). This intermediate underwent facile intersystem crossing (ISC) to the singlet surface (HSiGeH 3 ; 1 i1 ). The latter isomerized via at least three hydro-gen atom migra-tions involving exotic, hydrogen bridged reaction intermediates eventually leading to the H 3 SiGeH isomer i5 . This intermediate could undergo unimolecular decomposition yielding the dibridged butterfly-structured isomer 1 p1 (Si(µ-H 2 )Ge) plus molecular hydrogen through a tight exit transition state. Alternatively, up to two subsequent hydrogen shift to i6 and i7 , followed by fragmentation of each of these intermediates, could also form 1 p1 (Si(µ-H 2 )Ge) along with molecular hydrogen. The overall non-adiabatic reaction dynamics provide evidence on the existence of exotic dinuclear hydrides of main group XIV elements, whose carbon analog structures do not exist.