Substitution at saturated carbon. Part XVII. Substitution of tetraethyltin by mercury(II) carboxylates in methanol

Abstract
Observed second-order rate constants for the SE2 substitution of tetraethyltin by mercury(II) carboxylates, Hg(OCOR)2, in methanol increase along the series R = But < Et < Me < Ph < ClCH2CH2 < MeOCH2 < ClCH2. From the observed rate constants and the corresponding Hg2+–RCO2 stability constants, actual rate constants have been calculated for attack of various mercury(II) species on tetraethyltin; it is shown that under the kinetic conditions ca. 60% reaction takes place through the species Hg(OCOR)2. Rate constants for attack of Hg(OCOR)3 , Hg(OCOR)2, and HgOCOR+ are in order 0:1:102, and for substitution by both Hg(OCOR)2 and HgOCOR+ the calculated rate constants yield the above reactivity sequence in R (R = But < Me < MeOCH2). It is suggested that substitution of tetraethyltin by the species Hg(OCOR)2 in methanol takes place by the SE2(open) mechanism, and not through a cyclic transition state.

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