Tetranuclear group 7/8 mixed-metal and open trinuclear group 7 metal carbonyl clusters bearing bridging 2-mercapto-1-methylimidazole ligands

Abstract

The reactivity of group 7 metal dinuclear carbonyl complexes [M-2(CO)(6)(mu-SN2C4H5)(2)] (1, M = Re; 2, M = Mn) toward group 8 metal trinuclear carbonyl clusters were examined. Reactions of 1 and 2 with [Os-3(CO)(10)(NCMe)(2)] in refluxing benzene furnished the tetranuclear mixed-metal clusters [Os3Re(CO)(13)(mu(3)-SN2C4H5)] (3) and [Os3Mn(CO)(13)(mu(3)-SN2C4H5)] (4), respectively. Similar treatment of 1 and 2 with Ru-3(CO)(12) yielded the ruthenium analogs [Ru3Re(CO)(13)(mu(3)-SN2C4H5)] (5), and [Ru3Mn(CO)(13)(mu(3)-SN2C4H5)] (6), but in the case of 2 a secondary product [Mn-3(CO)(10)(mu-Cl)-(mu(3)-SN2C4H5)(2)] (7) was also formed. Compounds 3-6 have a butterfly core of four metal atoms with the M (Mn or Re) at a wingtip of the butterfly and containing a noncrystallographic mirror plane of symmetry. This result provides a potential method for the synthesis of a series of new group 7/8 mixed metal complexes containing a bifunctional heterocyclic ligand. Compound 7 is a unique example of a 54-electron trimanganese complex having bridging 2-mercapto-1-methylimidazolate and chloride ligands. Interestingly, the reaction or 1 with Fe-3(CO)(12) at 70-75 degrees C furnished the tri- and dirhenium complexes [Re-3(CO)(10)(mu-H)(mu(3)-SN2C4H5)(2)] (8) and [Re-2(CO)(6)(N2C4H5)(mu-SN2C2H5)(2)] (9), respectively instead of the expected formation of the mixed-metal clusters. The former is an interesting example of a 52-electron trirhenium-hydridic complex containing bridging 2-mercapto-1-methylimidazolate ligand, while the latter can be viewed as a 1-methylimidazole adduct of 1. No mixed Fe-Re complexes were produced in this reaction. The molecular structures of the new compounds 3-5 and 7-9 were established by single-crystal X-ray diffraction analyses and the DFT studies of compounds 5, 7 and 8 are reported.