Platinum arylthiolate complexes in different oxidation states

336 Abstracts

G15

PLATINUM ARYLTHIOLATE COMPLEXES IN D I F F E R E N T O X I D A T I O N STATES

Ren~ Ruppert a'b, Bernt Krebs b and Jan Reedijk a aLeiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands bAnorganisch-Chemisches Institut, Universitiit Miinster, Wilhelm-Klemm-Strafle 8, D-48149 Miinster, Germany Several enzymes, which contain partly sulfur-coordinated nickel as the active site catalyse different redox reactions in biological systems [1]. These reactions usually involve a change of the oxidation state of the metal. The heavier homologues of nickel, palladium and platinum and their compounds are well established as catalysts in industrial and general chemistry. Nevertheless, these metals usually do not show any catalytic or redox activity when they are mainly coordinated by sulfur ligands. Hitherto platinum thiolate complexes with the metal in the formal oxidation state +3 has not been described. The present work describes the synthesis and the crystal structures of two pairs of single-cored platinum complexes which contain either Pt(II) or Pt(III) in the same ligand environment. The oxidation of the platinum(H) complexes was performed with molecular oxygen. The unusual reaction of (Et4N)2[Pt(S2C6H4)2] with dioxygen to lead to the platinum(III) complex is probably due to the redox activity of the ligand 1,2-benzenedithiolate. In contrast to this the ligand 2,4,6-triisopropylthiophenolate (tip) in the complex [Pt(tiP)4][Na4(MeOH)8]4(tiP)2 cannot show such redox activity due to steric demands. UV-vis spectroscopy, cyclic voltammetry, various NMR techniques, magnetic measurements and EPR showed, that in this case the unusual reactivity towards dioxygen is caused by the sodium ions in the structure (see figure). This contact ion pair is maintained in apolar solvents like benzene. The platinum(I~ complexes (Et4N)[Pt(S2C6H4)2] and (PPh4)[Pt(tiP)4] show slightly shorter Pt-S-distances, but nearly the same geometry as the corresponding platinum(H) complexes. They are stable towards dioxygen and hydrolysis and show reversible redox behaviour in dmso solution.

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B.Krebs, G.Henkel, Angew. Chem., Int. Ed. Engl., 1991, 30, 769