Gas Phase Preparation of the Elusive Monobridged Ge(μ-H)GeH Molecule through Nonadiabatic Reaction Dynamics.

The hitherto elusive monobridged Ge(μ-H)GeH (X 1 A') molecule was prepared in the gas phase by bimolecular reaction of atomic germanium with germane (GeH 4 ). Electronic structure calculations revealed that this reaction commenced on the triplet surface with the formation of a van der Waals complex, followed by insertion of germanium into a germanium-hydrogen bond over a submerged barrier to form the triplet digermanylidene intermediate (HGeGeH 3 ); the latter underwent intersystem crossing from the triplet to the singlet surface. On the singlet surface, HGeGeH 3 predominantly isomerized through two successive hydrogen shifts prior to unimolecular decomposition to Ge(μ-H)GeH isomer, which is in equilibrium with the vinylidene-type (H 2 GeGe) and dibridged (Ge(μ-H 2 )Ge) isomers. This reaction leads to the formation of cyclic dinuclear germanium molecules, which do not exist on the isovalent C 2 H 2 surface, thus deepening our understanding of the role of nonadiabatic reaction dynamics in preparing nonclassical, hydrogen-bridged isomers carrying main group XIV elements.