Aromatic substitution. Part 1. Kinetics of reaction of phenyltriethyltin with mercury(II) salts in methanol


Reaction of PhSnEt3 with mercury(II) salts in methanol follows second-order kinetics, first-order in each reactant, and yields only PhHgX and Et3SnX. It is shown that the reactivity order in the mercury(II) species is Hgl3- ≪ Hgl2 < HgCl 2 < Hg(OAc)2. Under the investigated conditions, mercury(II) chloride reacts only via the covalent species HgCl2 and not via species such as HgCl+. Comparison with related aliphatic substitutions shows that a phenyl group is cleaved from tin by mercury(II) halides some 4 × 102 times as fast as a methyl group and 1 × 105 times as fast as an ethyl group. Added water mildly accelerates reaction of PhSnEt3 with HgCl2, whilst inert salts retard reaction; the activation energy is quite low, and it is suggested that reaction takes place via an intermediate π-complex through a transition state that is not particularly polar.

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Journal of the Chemical Society, Perkin Transactions 2