Time-resolved, Gas-phase Kinetic and Quantum Chemical Studies of the Reaction of Germylene with Hydrogen Chloride.

Abstract

Time-resolved studies of germylene, GeH2 , generated by laser flash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene at 193 nm and monitored by laser absorption, have been carried out to obtain rate constants for its bimolecular reaction with HCl. The reaction was studied in the gas phase, mainly at a total pressure of 10 Torr (in SF6 bath gas) at five temperatures in the range 295-558 K. Experiments at other pressures showed that these rate constants were unaffected by pressure. The second-order rate constants at 10 Torr (SF6 bath gas) fitted the Arrhenius equation: log(k/cm3 molecule-1 s-1 )=(-12.06±0.14)+(2.58±1.03 kJ mol-1 )/RTln10 where the uncertainties are single standard deviations. Quantum chemical calculations at G4 level support a mechanism in which an initial weakly bound donor-acceptor complex is formed. This can then rearrange and decompose to give H2 and HGeCl (chlorogermylene). The enthalpy barrier (36 kJ mol-1 ) is too high to allow rearrangement of the complex to GeH3 Cl (chlorogermane).