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 M₂(CO)₁₀ (M = Re, Mn) with pyrimidine-2-thiol (pymSH) in the presence of Me₃NO afford the tetranuclear square-type complexes [M₄(CO)₁₂(μ-κ³-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)(κ²-pymS)] (3) in which the pyrimidine-2-thiolate coordinates in a bidentate fashion. With diamines [M(CO)₃(κ²-L)(κ¹-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(κ¹-pymS)(κ²-dppm)] (8) and [Re(CO)₂(κ²-pymS)(κ¹-dppe)₂] (10), respectively, whereas 2 affords [Mn(CO)₂(κ²-pymS)(κ¹-dppm)₂] (9) and [Mn(CO)₂(κ²-pyS)(κ²-dppe)] (11) under similar conditions. Reactions of 1–2 with [Os₃(CO)₁₀(NCMe)₂] affords mixed-metal butterfly clusters [MOs₃(CO)₁₃(μ₃-κ²-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 Ru₃(CO)₁₂, carbon–sulfur bond cleavage occurs to give the tetranuclear clusters [MRu₃(CO)₁₄(μ₄-S)(μ-κ¹:η¹-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.