THE REACTIVITY OF COMPLEXES CONTAINING THE [MO-3(MU-S-3)(MU-S-2)(3)](4+) CORE - LIGAND SUBSTITUTION, SULFUR ELIMINATION AND SULFIDE BINDING

The reactivity of complexes, containing the [Mo-3(mu(3)S)(mu S-2)(3)](4+) core, was investigated in solution. Three types of electrophilic centers, (i) the three Mo atoms, (ii) the three equatorial (in plane) and (iii) the three axial (out of plane) sulfur atoms of the disulfido bridges, interact distinctly different with nucleophilic agents. The selective reactivity enabled the specific synthesis of new complexes containing either the [Mo-3(mu(3)S)(mu S-2)(3)](4+) or the [Mo-3(mu(3)S)(mu S)(3)](4+) cores by using (NEt(4))(2)[Mo3S(S-2)(3)Br-6] as starting material. A combination of sulfur abstraction and ligand substitution resulted in the formation of complexes of the composition [Mo(3)S(4)L(3)](4+), where L represents the tridentate N,O donors 1,3,5-triamino-1,3,5-trideoxy-cis-inositol and 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol. The complexes were characterized by one- and two-dimensional NMR spectroscopy and FAB mass spectrometry. In the presence of a weak base and 6-mercaptopurine (Hmp) or 8-hydroxyquinoline (Hoxq), the six Br atoms were replaced by these bidentate ligands forming [Mo3S(S-2)(3)(oxq)(3)](+) and [Mo3S(S-2)(3)(mp)(3)](+). In addition, the three oxq ligands could be quantitatively replaced by diethyldithiocarbamate (dtc(-)) in the presence of a slight excess of Na(dtc). The [Mo3S(S-2)(3)](4+) core was not affected under the harsh reaction conditions, but S2- was liberated by hydrolysis of dtc(-). The formed S2- anion was bound selectively to the three S-ax atoms of the [Mo3S(S-eq-S-ax)(3)](4+) core, resulting in the formation of the dimer [Mo3S(S-2)(3)(dtc)(3)]S-2. The dimeric structure was established by X-ray analysis, exhibiting a hexacoordinated S2- atom with a rather short average S-ax-S2- distance of 2.71 Angstrom and an elongated S-eq-S-ax distance of 2.11 Angstrom. Space group Aba2, a=17.48(1), b=26.13(2), c=16.489(8) Angstrom, Z=4, R=0.051.