Electron-transfer induced cleavage and formation of C-H-bonds in 17ē and 19ē platinum complexes

Abstract

The electrochemical behavior of platinum complexes [Pt(η⁴-diene)(η⁵-C₅R₅)]⁺BF₄ ⁻ (1 ⁺, diene = C₅Me₅H, R = H;2 ⁺, diene = C₅Me₅H, R = Me;3 ⁺, diene = C₆H₈, R = Me;4 ⁺, diene = C₈H₁₂, R = Me) was studied by cyclic voltammetry. Complexes1 ⁺ and2 ⁺ are shown to be capable of both oxidation and reduction. One-electron reduction of2 ⁺ gives a mixture of two neutral isomeric complexes5a,b of η³-allylic and σ,π,-olefinic type due to the cleavage of C-H bonds in the methyl groups of the pentamethylcyclopentadiene ligand of 19ē complexes2. The preparative electrochemical oxidation of2 ⁺ results in cleavage of the C-H bond at the sp³-hybridized pentamethylcyclopentadiene carbon atom in 17ē dication radical2 ²⁺ to give the decamethylplatinocene dication [Pt(η⁵-C₅Me₅)₂]²⁺(BF₄)₂ (7 ²⁺). It is shown that one-electron reduction of7 ²⁺ and one-electron oxidation of5a,b is accompanied by the formation of C-H bonds to form2 ⁺.