A Heterobimetallic Approach To Stabilize the Elusive Disulfur Radical Trianion (Subsulfide) S2•3-

A unique heterobimetallic disulfur monoradical, complex 2, with a diamond-shaped {NiS2Pt} core has been synthesized by two-electron reduction of a supersulfido-(nacnac)nickel(II) complex (nacnac=&beta-diketiminato) with [Pt(Ph3P)(2)(&eta(2)-C2H4)] as a platinum(0) source and isolated in 82% yield. Strikingly, the results of DFT calculations in accordance with spectroscopic (EPR, paramagnetic NMR) and structural features of the complex revealed that the bonding situation of the S-2 ligand is between the elusive half-bonded S-2 radical trianion (S-2(&Bull3-)) and two separated S2- ligands. Accordingly, the Ni-II center is partially oxidized, whereas the Pt-II site is redox innocent. The complex can be reversibly oxidized to the corresponding Ni,Pt-disulfido monocation, compound 3, with a S-S single bond, and reacts readily with O-2 to form the corresponding superoxonickel(II) and disulfidoplatinum(II) (4) complexes. These compounds have been isolated in crystalline form and fully characterized, including IR and multi-nuclear NMR spectroscopy as well as ESI mass spectrometry. The molecular structures of compounds 2-4 have been confirmed by single-crystal X-ray crystallography.