A general synthetic route for platinum sulphur dioxide cluster compounds and the X-ray structural characterisation of di-µ-carbonyl-carbonyl-tri(µ-sulphur dioxide)-tetrakis(triphenylphosphine)pentaplatinum–dichloromethane–propan-2-ol (1/2/1), [Pt5(CO)(µ-CO)2(µ-SO2)3(PPh3)4]·2CH2Cl2·Me2CH(OH)

Abstract

Some or all of the carbonyl ligands in platinum carbonyl phosphine clusters may be replaced by sulphur dioxide under mild conditions to give high yields of clusters containing the bridging sulphur dioxide ligand. In some cases ligand substitution is accompanied by a change in cluster structure which gives rise to high-yield routes for altering the nuclearity of platinum carbonyl clusters. In particular the reaction of sulphur dioxide with [Pt₄(µ-CO)₅(PMe₂Ph)₄] gave the trinuclear cluster [Pt₃(µ-SO₂)₃(PMe₂Ph)₃] rather than the tetranuclear cluster reported by us in an earlier communication. The molecular structure of [Pt₅(CO)(µ-CO)₂(µ-SO₂)₃(PPh₃)₄]·2CH₂Cl₂·Me₂-CH(OH) has been determined by single-crystal X-ray techniques. The compound crystallises in the triclinic space group P with two formula units in a unit cell with a= 13.991(6), b= 14.625(5), c= 21.285(4)Å, α= 84.07(2), β= 83.34(3), and γ= 70.76(4)°. The structure was solved to R 0.059 (R′ 0.079) from 7 033 observed independent reflections [F² 3.0 σ(F²)] collected in the range 3 ⩽ 2θ⩽ 45°. The molecule has an edge-bridged tetrahedral skeletal geometry with Pt–Pt in the range 2.751(1)–2.877(1)Å. The cluster has one terminal carbonyl and four triphenylphosphine ligands and two edges of the cluster are bridged by carbonyl ligands and three by sulphur dioxide. The other two edges are unbridged. Detailed analysis of the structure has clarified the nature of the bonding in pentanuclear platinum clusters and enabled the structure of a previously incorrectly characterised platinum arsine cluster to be reformulated.