Two geometrical isomers of the five-coordinate Platinum(II) complex [PtBr(SePh)(2,9-dimethyl-1,10-phenanthroline)(dimethylmaleate)]

The oxidative addition of phenylselenium bromide to three-coordinate Pt(0) complex [Pt(2,9-dimethyl-1,10-phenanthroline)(dimethylmaleate)] affords the corresponding five-coordinate Pt(II) complex having trigonal-bipyramidal coordination geometry. The product of the reaction exists as two geometrical isomers (rotamers): in the kinetically favoured compound the olefin substituents are on the same side of the bromide ligand, while the most thermodynamically stable isomer holds the same substituents pointing at the phenylselenenide ligand. The crystal structure of the two isomers is reported and discussed with respect to the reaction mechanism and thermodynamic stability.