Kinetico-mechanistic studies on the formation of seven-membered [C,N]-platinacycles: the effect of methyl or fluoro substituents on the aryl ancillary ligands

Abstract

The reactions of dinuclear [Pt₂(4-RC₆H₄)₄(μ-SEt₂)₂] (R = Me or F), or mononuclear [Pt(4-RC₆H₄)₂(SMe₂)₂] (R = Me or H), platinum(II) compounds with imines of the general formula 2-X,6-YC₆H₃CHNCH₂Ph (X = Br, Y = F; X = Cl, Y = F; X = Br, Y = H) produced seven-membered [C,N]-platinacycles. The reaction consists of the initial formation of cyclometallated platinum(IV) compounds followed by a three step process: reductive elimination, isomerisation of the resulting non-cyclometallated intermediate and a final cycloplatination process. Combined ¹H NMR and UV-Vis kinetico-mechanistic studies indicated that the rate determining step of the process depends on the nature of the aryl-Pt ligand (phenyl, p-tolyl or p-fluorophenyl).