C-H activation by aqueous platinum complexes: A mechanistic study

Article abstract of DOI:10.1016/0022-328X(95)05567-9

Detailed mechanistic studies are reported on the oxidation of alkanes by aqueous ^2-/^2- to alcohols plus alkyl chlorides, via proposed (alkyl)Pt^II and (alkyl)Pt^IV intermediates.Reactions of ^2- with RI (R = CH3, CH2CH2OH) in water yield ^2-, which were isolated as their NMe4 salts.Kinetic rate laws of their decomposition in aqueous chloride solution to ROH and RCl support S_N2 displacement by Cl^- or H2O as the mechanism of the last step. erythro- and threo-^2- are obtained by oxidation of ^- respectively, and react with Cl^- with inversion of stereochemistry at carbon, consistent with the S_N2 mechanism. ^2- is also obtained by oxidation of Zeise's salt with ^2-.Kinetics indicate that attack of water on coordinated ethylene to give a β-hydroxyethyl group precedes oxidation of Pt^II to Pt^IV, rather than the reverse order, and that this reaction is a model for the oxidation of (alkyl)Pt^II to (alkyl)Pt^IV during alkane functionalization. 195Pt isotopic labeling demonstrates that the oxidation is not accompanied by transfer of the β-hydroxyethyl group from one Pt center to another. Keywords: Platinum; C-H activation