OCTAMOLYBDENUM OXO-PYRAZOLATE CLUSTERS - SYNTHESES, CHARACTERIZATION, AND CRYSTAL AND MOLECULAR-STRUCTURES OF THE MO(V)/MO(VI) AND MO(VI) OCTAMOLYBDENUM CLUSTERS MO8(PZ)6O18(PZH)6 AND MO8(PZ)6O21(PZH)6

Two octamolybdenum compounds, containing both bridging pyrazolate and terminal pyrazole ligands, have been prepared by the reaction of molten pyrazole with molybdenum oxides, and their structures have been determined by single-crystal X-ray diffraction. Crystals of Mo8(pz)6O18(pzH)6.2pzH (1;pzH=pyrazole, C3H4N2; pz = pyrazolate anion, C3H3N2) are monoclinic, space group C2/c, with a = 23.026(3) angstrom, b = 13.345(3) angstrom, c = 23.314(2) angstrom, = 114.827(8)., and Z = 4; and those of Mo8(pz)6O21(pzH)6.3pzH.1/2H2O (2) are trigonal, space group R3BAR a = 20.005(2) angstrom, c = 30.567(5) angstrom, and Z = 6. The structures were solved by Patterson methods and were refined by full-matrix least-squares procedures to R = 0.026 and 0.030 for 9557 and 3683 reflections with I greater-than-or-equal-to 3sigma(I), respectively. The octamolybdenum species in 1 contains both Mo(VI) and Mo(V) ions, with the latter linked in pairs by metal-metal single bonds. Compound 2 involves a single-valent Mo(VI) octamolybdenum species and is photosensitive.