New Mixed-Metal Carbonyl Complexes Containing Bridging 2-Mercapto-1-methylimidazole Ligand

Reaction of [Mn-2(CO)(10)] with 2-mercapto-1-methylimidazole in the presence of Me3NO at 25 degrees C afforded two new dimanganese complexes [Mn-2(CO)(6(mu-)SN2C4H5)(2)] [Mn-2(CO)(7)(mu-SN2C4H5)(2)] (2). Compound I consists of two mu-SN2C4H5 ligands. each bound through the sulfur atom to two Mn atoms and through the nitrogen atom to one Mn atom forming a four-membered chelate ring. Compound 2 was found to consist of one mu-SN2C4H5 I ligand in a similar bonding mode to I but another mu-SN2C4H5 ligand coordinateS through the sulfur atom to one Mn atom and through the nitrogen atom to another Mn atom. Compound I was also obtained as the only product from the reaction of [Mn-2(CO)8(NCMe)(2)] with 2-mercapto-l-methylimidazole. In contrast, a similar reaction of [Re-2(CO)(8)(NCMe)(2)] with 2-mercapto-l-methylimidazole led to the formation of the di-, tri-, and tetranuclear complexes [Re3(CO)(8) (mu-CO)(mu(3)-SN2C4H5)(2)(mu-H)] (3), [Re-4(CO)(12)(mu-SN2C4H5)(4)] (4), and [Re-2(CO)(6)(mu-SN2C4H5)(2)] (5). Compound 3 provides a unique example of a hydrido trirhenium compound. The reaction of [Cr(CO)(3)(NCMe)(3)] and [Mo(CO)(3)(NCMe)(3)] with 1 in refluxing THF afforded the mixed metal complexes [CrMn2(CO)(8)(mu-CO)(2) (mu(3)-SN2C4H5)(2)] (6) and [MoMn2(CO)(8)(mu-CO)(2)-(mu(3)-SN2C4H5)(2)] (7), respectively, in which two Mn-M (M = Mo, Cr) bonds were formed. In contrast, a similar treatment of [W(CO)(3)(NCMe)(3)] with 1 yielded two W-Mn complexes [Mn2W(CO)(8)(mu-CO)(2)(mu(3)-SN2C4H5)(2)] (8) and [Mn2W(CO)(7)(mu-CO)(2)(SN2C4H5)(mu(3)-SN2-C4H5)(2)] (9). Treatment of 1 with [Fe-3(CO)(12)] at 70-75 degrees C afforded the trinuclear mixed-metal complex [FeMn2(Co)(8)(mu-Co)(mu(3)-SN2C4H5)(2)] (10) and the diiron side product [Fe-2(CO)(6)(mu-S2N2C4H5)(2)] (11). Compounds 6-10 have a bent open structure of three metal atoms linked by two metal-metal bonds and all, except 9 and 10, contain a noncrystallographic two-fold axis of symmetry. Compound 9 is structurally similar to 8. but it contains a SN2C4H6 ligand, mono coordinated through the exocyclic sulfur atom to the W atom and a Mn-Mn bond instead ora Mn-W bond. Compound 11 comprises two bridging S2N2C4H5 ligands, which arise from the coupling of 2-mercapto-1-methylimidazole with sulfur.