Synthesis of monoorganotin(IV) chloride complexes of cis-1,2-bis(diphenylphosphino)ethylene: Solution and solid state structures

Organotin(IV) complexes of the type [RSnCl₃(cis-Ph₂PCHCHPPh₂)] [R = Me (1), ⁿBu (2), Ph (3)] were prepared by the reaction of RSnCl₃ with the rigid bisphosphine ligand, cis-1,2-bis(diphenylphosphino)ethylene in dichloromethane. The complexes have been characterized both in solution and the solid state. Low temperature ³¹P and ¹¹⁹Sn NMR studies indicate two different phosphorus environments. The crystal structures indicate a weak but chelating mode of coordination of the two phosphorus atoms to tin, leading to a distorted octahedral geometry. In solution the complexes 1-3 undergo a redistribution reaction to form [SnCl₄(cis-Ph₂PCHCHPPh₂)] (4) as one of the products. In order to confirm the redistribution, complex 4 has been prepared separately and characterized both structurally and spectrally.