σ-Bonded organotransition-metal ions. Part III. Displacement of chromium by mercury: five-co-ordinate chromium(III) as a leaving group
- 1 January 1966
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 1805-1810
- https://doi.org/10.1039/j19660001805
Abstract
The kinetics of the reaction of mercuric chloride with six penta-aquopyridiomethylchromium(III) ions in aqueous solution have been investigated. The changes in rate in the presence of added chloride ion are ascribed to reaction through the ions HgCl3 – and HgCl4 2– for which rate coefficients have been calculated. The products of these reactions are the corresponding pyridiomethylmercuric chloride ions and the hexa-aquochromium(III) ion together with chloropenta-aquochromium(III) ion at high chloride-ion concentrations. The formation of these chromic ions can be accommodated on the basis of the capture of a five-co-ordinate chromium(III) ion by chloride ion or solvent water. This, together with the kinetic form of the reactions and the order of reactivity of the pyridiomethylchromium(III) ions (4- > 3- > 2-), shows that the reactions involve the direct (SE2) displacement of chromium(III) by mercury(II). Similar reactions have been studied with mercuric bromide, which, in the presence of added bromide ion, also reacts through the ions HgBr3 – and HgBr4 2–, and with mercuric nitrate and acetate.Keywords
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