Mechanism and stereochemistry for nucleophilic attack at carbon of platinum(IV) alkyls: model reactions for hydrocarbon oxidation with aqueous platinum chlorides

Abstract

We and others have recently confirmed the original reports by Shilov that aqueous solutions of a mixture of [PtCl_4]^(2-) and [PtCl_6]^(2-) are capable of functionalizing the C-H bonds of substrates including methane, initially producing a mixture of alcohols and alkyl chlorides. The working mechanistic scheme invokes the following general features: (1) electrophilic C-H activation to generate a platinum(I1) alkyl, (2) oxidation to a platinum(1V) alkyl, and (3) nucleophilic attack by water or chloride, displacing platinum(II) and generating the product alcohol or alkyl chloride. In this article we report the preparation, isolation, and characterization of methyl and β-hydroxyethyl derivatives of chloroplatinum(IV) along with the results of our investigations of the mechanism for nucleophilic attack by water or chloride. The rates and stereochemistry provide some of the first firm support for the latter stages of this working mechanistic scheme.