MECHANISTIC STUDIES ON NOVEL MO-S CONTAINING CLUSTER COMPLEXES IN AQUEOUS-SOLUTION

Studies on Mo-S cluster complexes including cuboidal [Mo4S4H2O)12]n+ ( n = 4,5,6) and heterometallic [Mo3MS4(H2O)x]4+ (x = 10, 12) complexes are described. Such cubes are stable in aqueous solution, and provide a ready means of studying redox and substitution reactions not possibl e in the case of e.g. Fe4S4 complexes. Here the emphasis is on substit ution reactions. Studies on two heterometallic cubes M = Ni, Cr obtain ed from [Mo3S4(H2O)9]4+ are reported. Whereas [Mo3NiS4(H2O)10]4+ conta ins tetrahedral Ni, the [Mo3CrS4(H2O)12]4+ cluster has octahedral Cr. Using the tridentate 1,4,7-triazacyclononane ligand, 9-aneN3, the cube [Mo3Ni(9-aneN3)S4(H2O)9]4+ has been prepared containing an octahedral and inert Ni. The case for a Ni-degrees assignment is considered. The crystallographically characterised [Mo3S7Br6]2- has been converted to a new aqua ion [Mo3S7(H2O)6]4+. With P(C6H4SO3)3(3-) in 2M Hpts the l atter gives [Mo3S4(H2O)9]4+. Two stages are observed in substitution s tudies with NCS-.