Theoretical Study of the Heterolytic σ Bond Cleavage on the Ge═O Bond of Germanone. An Insight into the Driving Force from Both Electronic and Dynamical Aspects.

Abstract

The mechanism of the σ bond cleavage of H2O, NH3, Me2C═O, H2, CH4, BH3, and SiH4 on the Ge═O bond of germanone is examined by means of both quantum mechanical (QM) and molecular dynamics (MD) methods. The QM calculations show that the σ bonds of all the substrates are heterolytically broken on the very largely polarized Ge═O bond. Before the σ bond cleavage, the substrate at first approach the Ge═O germanium in the cases of H2O, Me2C═O, and NH3, and in contrast, the Ge═O oxygen in the cases of H2, CH4, BH3, and SiH4. For the cases of H2O, NH3, and Me2C═O, a cluster in which the substrate coordinates to the Ge exists before the σ bond cleavage, and this coordination of the substrate plays an important role on the heterolytic σ bond cleavage. The QM-MD simulations are also conducted for the case of H2O, and they show that the kinetic energy of the H2O-coordinated cluster especially concentrates on the coordinated H2O oxygen to strongly oscillate the coordinate bond between the H2O oxygen and the Ge. This oscillation further enlarges just before the O-H σ bond cleavage, and the kinetic energy of this oscillation would be transmitted to the normal mode of the O-H bond breaking. Thus, the coordination and the vibration of the H2O oxygen was thought to be an important driving force of the heterolytic cleavage of the O-H σ bond in both electronic and dynamical aspects.