Oxidation of a Pt 2 (µ-SO 2 ) moiety to µ-SO 3 and the crystal structure of [Pt 2 (µ-SO 3 )(µ-SO 2 )(C 8 H 12 ) 2 ]

Bis(cyclo-octa-1,5-diene)platinum(0) as a solid has been found to react immediately with SO2giving [Pt2(µ-SO2)2(C8H12)2], (1). N.m.r. spectroscopy reveals that the two C8H12 ligands in the dimer (1) have three co-ordinated olefinic groups with the remaining one not co-ordinated. The presence of µ-SO2 ligands is consistent with the i.r. spectrum. Solutions of complex (1) are oxidized slowly by atmospheric O2to give the novel µ-SO3 complex [Pt2(µ-SO3)(µ-SO2)(C8H12)2], (2). Complex (2) was characterized by single-crystal X-ray crystallography and consists of two distorted square-planar platinum(II) fragments held together by a bridging SO22– anion and a bridging SO32– anion. The bond parameters at both Pt atoms indicate a square-planar co-ordination geometry and a value of 20.1° is calculated for the dihedral angle between the two square-planar fragments. The µ-SO2 ligand is σ-bonded to both Pt atoms through the S atom while the µ-SO3 ligand is σ-bonded to one Pt atom by the S atom and to the other metal via an O atom. The two Pt, the two S, and the O atoms form a puckered five-membered ring.