The NMR spectroscopic and X-ray crystallographic study of the oxidative addition of bis(2-thienyl) diselenide to zerovalent palladium and platinum centers

The pathway of the reaction of dithienyl diselenide with tetrakis(triphenylphosphine)palladium(0) and -pratinum(0) has been explored by the use of NMR spectroscopy and X-ray diffraction. The oxidative addition of dithienyl diselenide to [Pd(PPh3)(4)] mainly results in the formation of two isomers of dinuclear [Pd-2(SeTh)(4)(PPh3)(2)] (Th = 2-thienyl, C4H3S) complex. The workup of the solution produced X-ray-quality crystals of trans-[Pd-2(SeTh)(4)(PPh3)(2)]. The corresponding reaction with [Pt(PPh3)(4)], however, affords isomers of mononuclear [Pt(SeTh)(2)(PPh3)(2)]. Upon recrystallization from dichloromethane a small amount of crystals of dinuclear [Pt-2(SeTh)(4)(PPh3)(2)] is obtained together with those of trans-[Pt(SeTh)(2)(PPh3)(2)]. While the products from both reactions imply that the oxidative addition takes place with the cleavage of the Se-Se bond, a small amount of trans-[PdCl(Th)(PPh3)(2)] is formed in the reaction of [Pd(PPh3)(4)] and Th2Se2 in dichloromethane indicating that C-Se cleavage may also take place during the oxidative addition. (C) 1999 Elsevier Science S.A. All rights reserved.