Substitution of pyridine ligands from platinum(II) iodo complexes by dimethyl sulphoxide: crystal structure of trans-(3,5-dimethylpyridine)(dimethyl sulphoxide-S)di-iodoplatinum

Abstract

Dimethyl sulphoxide substitutes one pyridine or substituted pyridine (Xpy = pyridine, 4-methylpyridine, 3,5-dimethylpyridine, 4-chloropyridine, or 4-cyanopyridine) from cis-[Pt(Xpy)₂I₂] to form trans-[Pt(Xpy)(dmso)I₂] complexes. The dmso ligand is bound through the sulphur (from i.r. and ¹H n.m.r. spectra). The trans structure was confirmed by Pt–H coupling constants and an X-ray crystal structure determination of trans-[Pt(3,5Me₂-py)(dmso)I₂]. Crystals are orthorhombic, space group Pbca, with cell parameters a= 10.617(9), b= 17.052(6), c= 16.951 (6)Å, and Z= 8. The crystal structure was determined by standard methods and refined to R= 0.065 and R′ 0.087 based on 2 848 observed reflections. Co-ordination of the ligands is square planar with the bond distances Pt–N 2.08(2), Pt–S 2.233(5), and Pt–I 2.598(2), 2.613(2)Å.