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Stannanes as free-radical reducing agents: an ab initio study of hydrogen atom transfer from some trialkyltin hydrides to alkyl radicals

Dakternieks, D., Henry, D.J. and Schiesser, C.H. (1997) Stannanes as free-radical reducing agents: an ab initio study of hydrogen atom transfer from some trialkyltin hydrides to alkyl radicals. Journal of the Chemical Society, Perkin Transactions 2 (9). pp. 1665-1670.

Link to Published Version: http://dx.doi.org/10.1039/A701822C
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Abstract

Ab initio molecular orbital calculations using a (valence) double-ξ pseudopotential (DZP) basis set, with (MP2, QCISD) and without (SCF) the inclusion of electron correlation, predict that hydrogen atoms, methyl, ethyl, isopropyl and tert-butyl radicals abstract hydrogen atoms from stannane and trimethyltin hydride via transition states in which the attacking and leaving radicals adopt a colinear arrangement. Transition states in which (overall) Sn–C separations of 3.50 Å have been calculated; these distances appear to be independent of the nature of the attacking radical and alkyl substitution at tin. At the highest level of theory (QCISD/DZP//MP2/DZP), energy barriers (ωE1‡) of 18–34 kJ mol-1 are predicted for the forward reactions, while the reverse reactions (ωE2‡) are calculated to require 140–170 kJ mol-1. These values are marginally affected by the inclusion of zero-point vibrational energy correction. Importantly, QCISD and MP2 calculations predict correctly the relative order of radical reactivity toward reduction by stannanes: tert-butyl > isopropyl > ethyl. By comparison, SCF/DZP, AM1 and AM1(CI = 2) calculations perform somewhat more poorly in their prediction of relative radical reactivity.

Publication Type: Journal Article
Publisher: Chemical Society
Copyright: © Chemical Society
URI: http://researchrepository.murdoch.edu.au/id/eprint/4960
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