Vinylic Deprotonation in the Coordination Sphere of Platinum(II): Regioselective Formation of Alkenyl Complexes

Abstract

AbstractReaction of [PtCl(η2‐CH2=CHAr)(tmeda)](ClO4) (1) [Ar = C6H5 (1a), 4‐CH3OC6H4 (1b), 3‐NO2C6H4 (1c); tmeda = N,N,N′,N′‐tetramethylethylenediamine) with triethylamine, or even with inorganic carbonate, leads to the abstraction of a vinylic proton and formation of the (alkenyl)platinum species [PtCl{(E)‐CH=CHAr}(tmeda)] (2) in high yield. The initially formed (E) isomer, in solution of chlorinated solvents, partly isomerizes into the (Z) form [equilibrium ratio (E)/(Z) ≈︁ 4:1]; the isomerization reaction is rather slow and is catalyzed by visible light. The nature of the phenyl substituent (electron donor OMe or electron‐withdrawing NO2 group) does not appear to affect the rate of deprotonation. The nature and stereochemistry of the formed (alkenyl)platinum species has been elucidated through 1D and 2D 1H and 13C NMR spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)