Influence of light on the oxidative addition of bromine to trans-[PtCl2-(PEt3)2]: crystal structure of all-trans-[PtBr2Cl2(PEt3)2]

Abstract

Addition of bromine to trans-[PtCl₂(PEt₃)₂] in chloroform solution gives a single product, all-trans-[PtBr₂Cl₂(PEt₃)₂], provided that light is excluded. In the presence of light, halogen scrambling occurs to give a mixture of species [PtBr_xCl_4–x(PEt₃)₂], x= 0–4, with trans phosphines. Previously, the importance of light to this scrambling reaction had not been realized. In the dark, platinum(II) complexes trans-[PtCl₂(PEt₃)₂] or trans-[PtBr₂(PEt₃)₂] are poor at promoting halogen scrambling in trans-[PtBr₂Cl₂(PEt₃)₂], the structure of which has been determined by X-ray diffraction. Crystals are monoclinic with a= 9.414(2), b= 13.146(3), c= 8.656(1)Å, and β= 103.10(2)°. The molecule has a crystallographic centre of symmetry and the structure has been refined to a final R of 0.030 for 1 108 reflections.