Enthalpies and entropies of sublimation of germanium tetraphenyl and di-germanium hexaphenyl. The bond dissociation energy of GeC and GeGe

Abstract

The sublimation pressures of germanium tetraphenyl and di-germanium hexaphenyl in the temperature ranges 402 to 476 K and 483 to 558 K, respectively, have been determined from simultaneous measurements of the torsional recoil and the rate of mass effusion. The enthalpies and entropies of sublimation derived from the least-squares analyses of the results are: δH° sub ( GePh 4, c, 298.15 K )=(37.5±1) kcal th mol −1 ; δH° sub ( Ge 2Ph 6, c, 298.15 K )=(50±1) kcal th mol −1 ; δS° sub ( GePh 4, c, 445 K =(59.8±0.6) cal th K −1 mol −1 ; δS° sub ( Ge 2Ph 6, c, 520 K =(70.8±1) cal th K −1 mol −1 ; The average bond dissociation energies are calculated to be: <D>(Ge—Ph) GePh 4 =(73.7±0.8) kcal th mol −1 ; <D>(Ge—Ph) Ge 2Ph 6 =(70.4±0.7) kcal th mol −1 ; The bond dissociation energy D(Ph 3GeGePh 3) is estimated to be (58 ± 5) kcal th mol −1.