CH₃–X Reductive Elimination Reactivity of Pt^IVMe Complexes Supported by a Sulfonated CNN Pincer Ligand (X = OH, CF₃CO₂, PhNMe₂⁺)

Three new dihydrocarbyl LPt^IVMe­(Y) complexes (6–8; Y = Cl, I, OCH₂CF₃) supported by the sulfonated CNN pincer ligand L have been prepared and characterized. The reaction of these complexes with a number of nucleophiles (H₂O, CF₃CO₂^–, Me₂SO, PhNMe₂) resulting in the formation of corresponding C–X coupled products CH₃–X has been studied in 2,2,2-trifluoroethanol (TFE) and DMSO. In TFE or DMSO solutions at 22 °C, in the presence of PhNMe₂, a quantitative formation of a C–N coupled product, PhNMe₃⁺, was observed for 6–8, with the reactivity decreasing in the order 6 > 7 > 8. The use of NaO₂CCF₃ in TFE solutions was less efficient, leading to the production of MeO₂CCF₃ in 60% yield after 22 h at 70 °C. In DMSO the C–O coupling was high yielding when aqueous trifluoroacetic acid was used to produce methanol (87% after 3 h at 80 °C) or when NaO₂CCF₃ was used to form MeO₂CCF₃ (80% after 1.5 h at 80 °C), with Me₃SO⁺ being a minor byproduct. The kinetics study of the reaction between 6–8 and PhNMe₂ in TFE has revealed an overall second-order rate law, d­[PhNMe₃⁺]/dt = k₂[6, 7 or 8]­[PhNMe₂], consistent with the realization of an S_N2-type process. A DFT modeling of several alternative pathways of reaction between 7 and PhNMe₂ in TFE supported the direct nucleophilic attack of PhNMe₂ at the methyl group carbon of 7 as the most likely mechanism of this transformation.