SYNTHESIS, STRUCTURE, AND PROPERTIES OF OXIDIZED HEXAMOLYBDENUM CLUSTERS [(MO6X7Y)X'6]2- (X = X' = CL, BR, Y = S, SE)

The synthesis, structure, and properties of Mo6(13+) species, which are obtained by the oxidation of Mo6(12+) species [(Mo6X7Y)X'6]3- (X = X' = Cl, Br; Y = S, Se), are reported. (n-Bu4N)2[(Mo6Cl7S)Cl6] crystallizes in the monoclinic space group P2(1)/n with a = 18.542 (2) angstrom, b = 11.701 (2) angstrom, c = 12.806 (2) angstrom, beta = 90.21 (1)-degrees, V = 2778.5 (7) angstrom 3, and Z = 2. (n-Bu4N)2[(Mo6Cl7Se)Cl6] crystallizes in the monoclinic space group P2(1)/n with a = 18.571 (2) angstrom, b = 11.685 (1) angstrom, c = 12.845 (1) angstrom, beta = 90.12 (1)-degrees, V = 2787.1 (5) angstrom 3, and Z = 2. (n-Bu4N)2[(Mo6Br7S)Cl6] also crystallizes in the monoclinic space group P2(1)/n with a = 18.740 (2) angstrom, b = 11.647 (2) angstrom, c = 13.030 (2) angstrom, beta = 90.05 (1)-degrees, V = 2844.0 (7) angstrom 3, and Z = 2. The Mo6(12+) species (Et4N)3[(Mo6Br7S)Cl6] crystallizes in the tetragonal space group P4(2)/mnm with a = 11.968 (1) angstrom, c = 16.804 (2) angstrom, V = 2406.8 (4) angstrom 3, and Z = 2. The Mo-Mo distances of the Mo6(13+) clusters (2.626 (3) angstrom in [(Mo6Cl7S)Cl6]2-, 2.628 (3) angstrom in [(Mo6Cl7Se)Cl6]2-, 2.653 (3) angstrom in [(Mo6Br7S)Cl6]2-) are slightly longer than those of the corresponding Mo6(12+) species. Absorption peak positions in the 1800-nm (5320-6060 cm-1) and 900-nm regions (10 500-11 200 cm-1) are independent of the capping and terminal ligands, but those in the range 480-650 nm (15 400-20 400 cm-1) depend on the ligand. Their ESR spectra at 77 K are axially symmetric (g perpendicular-to = 2.12-2.15, g parallel-to = 2.05-2.07). The electronic structure is discussed on the basis of these data.