Isolation of the novel dirhodium(II/II) thiolate compound Rh2(η1-C6H5S)2(μ-C6H5S)2(bpy)2

The reaction of the anticancer active compound [Rh-2(mu-O2CCH3)(2)-(bPY)(2)(CH3CN)(2)][BF4](2) (1) (bpy = 2,2'-bipyridine) with NaC6H5S under anaerobic conditions yields Rh-2(eta(1)-C6H5S)(2)(mu-C6H5S)(2)(bPY)(2-) CH3OH (2), which was characterized by UV-visible, IR, and H-1 NMR spectroscopies as well as single-crystal X-ray crystallography. Compound 2 crystallizes as dark red platelets in the monoclinic space group C2/c with cell parameters a = 20.398(4) Angstrom, b = 11.861(2) Angstrom, c = 17.417(4) Angstrom, beta = 108.98degrees, V = 3984.9(14) Angstrom(3), Z = 4. The main structural features are the presence of a [Rh-2](4+) core with a Rh-Rh distance of 2.549(2) Angstrom bridged by two benzene thiolate ligands in a butterfly-type arrangement. The axial positions of the [Rh-2](4+) core are occupied by two terminal benzene thiolates. Cyclic voltammetric studies of 2 reveal that the compound exhibits an irreversible oxidation at +0.046 V in CH3CN, which is in accord with the fact that the compound readily oxidizes in the presence of O-2. The fact that this unusual dirhodium(II/II) thiolate compound is formed under these conditions is an important first step in understanding the metabolism of dirhodium anticancer active compounds with thiol-containing peptides and proteins.