The bonding,structure, and photochemistry of some stable and unstable germanium species

The ultraviolet and vacuum-ultraviolet photolyses of GeH₄, GeH₃Cl, GeH₂Cl₂, GeHCl₃, GeCl₄, GeH₃Br, and GeH₂Br₂ in argon and carbon monoxide matrices have been performed between 4° and 24° K. The results of these experiments support the successful isolation and characterization of a variety of germanium free-radical species produced as a result of primary and secondary photolytic processes. In order to control, characterize and understand the various elementary processes (photochemical and fragment diffusion) occurring in the matrix, both in situ photolysis as well as simultaneous deposition and photolysis were performed as a function of photolyzing radiation, temperature (of the cold window), and concentration (M/ R = matrix/reactive material).The identification and structure of the photochemically produced free radicals were obtained from the vibrational (infrared) spectrum before and after photolysis. In some cases, complete vibrational assignments were possible. Force field (normal coordinate) calculations were also performed in order to corroborate these assignments, within the limitation of their application to matrix isolated spectra.Finally, the structural and bonding properties of these free radicals, as reflected by their vibrational frequencies, are compared with similar stable and unstable Group IVA species in an effort to understand the major effect(s) controlling their geometry. The geometries obtained on the basis of the experimental observations are compared with those predicted by Walsh's semiempirical MO treatment and Self-Consistent Extended Huckel calculations. In addition, a simple thermodynamic argument in conjunction with elementary quantum mechanics is used as a tool for predicting the structure of some of these simple free-radical species.