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Vinyl‐ and ethynylsilanes, ‐germanes and ‐stannanes. A new case of dissociative proton attachment
Author(s) -
Mó Otilia,
Yáñez Manuel,
Gal JeanFrançois,
Maria Pierre Charles,
Guillemin JeanClaude
Publication year - 2002
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.498
Subject(s) - chemistry , protonation , acetylene , proton affinity , electronegativity , dissociation (chemistry) , density functional theory , proton , computational chemistry , ethylene , medicinal chemistry , crystallography , photochemistry , organic chemistry , ion , catalysis , physics , quantum mechanics
The gas‐phase protonation of H 2 CC(H)XH 3 and HC≡CXH 3 (X = Si, Ge, Sn) compounds was investigated through the use of high‐level density functional theory methods. The structures of neutral and protonated species were optimized at the B3LYP/6–31G* level of theory, while the final energies were obtained by single‐point B3LYP/6–311 + G(3df,2p) calculations. In the gas phase, vinyl‐ and ethynylsilanes, ‐germanes and ‐stannanes behave as carbon bases of moderate strength, with the only exception of vinylstannane, which is predicted to be about 20 kJ mol −1 more basic than ammonia. In all cases C α protonation is the most favorable process. This protonation is followed by a C—X bond cleavage, so that the protonated form corresponds to a tightly bound complex between ethylene (or acetylene) and the corresponding XH 3 + cation. This implies that dissociative proton attachments can be observed when the basic center is an atom of low electronegativity, provided that the other atoms bonded to it are much less electronegative than the basic center itself, and that the fragments formed as products of the dissociation are intrinsically stable. Copyright © 2002 John Wiley & Sons, Ltd.