Ab Initio and Density Functional Theoretical Studies of Structures, Vibrational Spectra, and Dimerization Dynamics of Simple Transient Germenes

Structures and harmonic vibrational frequencies for several simple transient germenes, H2GeCH2 (1), MeHGeCH2 (2), Me2GeCH2 (3), FHGeCH2 (4), and H2GeCHF (5), and their dimerization and transition state energies for the head-to-tail and head-to-head self-coupling have been calculated by ab initi...

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Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 1998-01, Vol.102 (4), p.744-753
Main Authors: Kudin, Konstantin N, Margrave, John L, Khabashesku, Valery N
Format: Article
Language:English
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Summary:Structures and harmonic vibrational frequencies for several simple transient germenes, H2GeCH2 (1), MeHGeCH2 (2), Me2GeCH2 (3), FHGeCH2 (4), and H2GeCHF (5), and their dimerization and transition state energies for the head-to-tail and head-to-head self-coupling have been calculated by ab initio HF 3-21G and 6-311G(d,p) and density functional theory B3LYP/6-311G(d,p) methods. The effect of substituents on the GeC bond lengths and bond orders, as well as frequencies and force constants of the GeC stretch, is predicted to be relatively small in germenes 1 − 3 and be substantially stronger in the F-substituted molecules 4 and 5. Within the limits of the HF/3-21G method, the head-to-tail cyclodimerizations of all studied germenes 1 − 5 were found to be more exothermic than the head-to-head processes and to proceed with very low or zero barriers. This conclusion is confirmed for 1 − 4 by the higher level calculations with the 6-311G(d,p) basis set at HF and B3LYP levels, which in the case of 5 leads to the opposite result such as a substantial barrier for the head-to-tail dimerization and a lesser exothermicity of this process relative to the head-to-head one. The comparison of the HF/3-21G data available for the whole series of similarly substituted silenes with those calculated for 1 − 5 at the same level of theory indicate somewhat easier dimerization of germenes with respect to their double-bonded silicon analogues.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp972006p