Synthesis, structure and reactivity of tetranuclear square-type complexes of rhenium and manganese bearing pyrimidine-2-thiolate (pymS) ligands: versatile and efficient precursors for mono- and polynuclear compounds containing M(CO)(3) (M = Re, Mn) fragments

Abstract

Reactions of M-2(CO)(10) (M = Re, Mn) with pyrimidine-2-thiol (pymSH) in the presence of Me3NO afford the tetranuclear square-type complexes [M-4(CO)(12)(mu-kappa(3)-pymS)(4)] (1, M = Re; 2, M = Mn). Both consist of four M(CO)(3) (M = Re, Mn) units, pairs of which are joined by tridentate pyrimidine-2-thiolate ligands. Treatment of 1-2 with a variety of donor ligands results in cleavage of the square to afford mononuclear species with either a mono-or bidentate pyrimidine-2-thiolate ligand. Triphenylphosphine reacts with 2 to give [Mn(CO)(3)(PPh3)(kappa(2)-pymS)] (3) in which the pyrimidine-2-thiolate coordinates in a bidentate fashion. With diamines [M(CO)(3)(kappa(2)-L)(kappa(1)-pymS)] (4-7) (M = Re, Mn; L = 2,2'- bipy, 1,10-phen, en) result in which the pyrimidine-2-thiolate binds in a monodentate fashion through sulfur. With diphosphines, complexes with different stoichiometries and pyrimidine-2-thiolate binding modes are obtained depending on the nature of the metal and diphosphine. With dppm and dppe, 1 gives [Re(CO)(2)(kappa(1)-pymS)(kappa(2)-dppm)] (8) and [Re(CO)(2)(kappa(2)-pymS)( (kappa(1)-dppe)(2)] (10), respectively, whereas 2 affords [Mn(CO)(2)(kappa(2)-pymS)(kappa(1)-dppm)(2)] (9) and [Mn(CO)(2)(kappa(2)-pyS)(kappa(2)-dppe)] (11) under similar conditions. Reactions of 1-2 with [Os-3(CO)(10)(NCMe)(2)] affords mixed-metal butterfly clusters [MOs3(CO)(13)(mu(3)-kappa(2)-pymS)] (12-13) in which the group 7 metal occupies a wing-tip position and the pyrimidine-2-thiolate ligand caps a triangular Os2M face. With Ru-3(CO)(12), carbon-sulfur bond cleavage occurs to give the tetranuclear clusters [MRu3(CO)(14)(mu(4)-S)(mu-kappa(1):eta(1)-pym)] (14-15) bearing both the extruded sulfur and the heterocyclic ring. The molecular structures of 1-7, 10 and 12 have been established by X-ray diffraction allowing the binding mode of the pyrimidine-2-thiolate ligands to be probed.