Michael Ardon

The structure of aqua-hydroxo double salts

Abstract The preparation and structure of two so-called aqua-hydroxo double salts of cobalt(III) are reported. X-ray structural analysis showed the compounds not to be double salts of two distinct mononuclear cations but to contain one binuclear cation in which the two equivalent cobalt atoms are bridged by a hydrogen oxide ligand (μ-H3O2). Compound 1, trans-{[Co(en)2NO2]2(H3O2)}(C1O4)3·2H2O forms monoclinic crystals, space group P21/n, with a = 12.098(2) A, b = 8.981(1) A, c = 14.415(2) A, β = 93.39(2)°, V = 1563(1) A3 and Z = 2. Compound 2, trans-{[Co(en)2NCS]2(H3O2)}(CF3SO3)3·H2O forms triclinic crystals, space group P 1 with a = 12.864(2) A, b = 14.429(2) A, c = 11. 177(1) A, α = 105.21(3)°, β = 100.33(2)°, γ = 65.96(2)°, V = 1822(1) A3 and Z = 2. The two structures were refined by least-squares methods to residuals of R = 0.077, Rw = 0.087 and R = 0.063, Rw = 0.069, respectively. In 1, the dimer resides on a crystallographic inversion center and the O⋯O separation in the H3O2 bridge is 2.412(9) A. In 2 there is no crystallographic symmetry imposed upon the dimer but the two CoO(H3O2) distances are identical within the experimental error. The O⋯O length in the H3O2 unit is 2.415(6) A.

Molybdenum aquo ions in solution

Abstract Five aquo ions of molybdenum have been separated and identified in recent years. These are [Mo 2 ] 4+ , [Mo(H 2 O) 6 ] 3+ , [Mo 2 (OH) 2 ] 4+ , [Mo 2 O 2 ] 4+ and [Mo 2 O 4 ] 2+ . The studies leading to the discovery and identification of these ions are reviewed. Ion exchange chromatography was the main tool for the isolation and characterisation of these ions. Earlier studies of the aquo ions of Mo(IV) and Mo(V) are also reviewed.

Structure and reactivity of an intermediate in the two-electron reduction of dimolybdenum(III) by a hydride ligand in the MoHMo system

Abstract The raaction between the μ-hydride dimolybdenum(III) complex [Mo2Cl8H]3− and carboxylic acids in aqueous solution produces a violet species which slowly decomposes to yield the quadruply bonded dimolybdenum(II) complex Mo2(O2CR)4. The violet intermediate in the reaction of [Mo2Cl8H]3− with glycine was isolated by ion exchange chromatography and crystallized. The crystals of [Mo2H(OH)(gly)2Cl4] (1) are monoclinic, space group P21/n with a = 9.536(4), b = 14.792(4), c = 9.339(3) A , β = 109.99(3)°, V = 1283(1) A 3 and Z = 4 . The two Mo(III) ions in this complex are bridged by one hydride ligand one OH− group and two glycine groups through the carboxylic end. The MoMo distance is 2.353(5) A, the shortest found for the MoHMo system. [(H2O)2MoH(OH)(gly)2Mo(H2O)2]4+ is the structure proposed for the violet intermediate II in the reaction 4 gly +[ Mo 2 Cl 8 H ] 3− → II → H + +[ Mo 2 ( gly ) 4 ] Cl 4 +4 Cl − This structure was derived from structure 1, the high ionic charge of about 4+ and the absence of chloride in this species. The decomposition reaction of II and the relation of II with the red intermediate III of the reaction [ Mo 2 Cl 8 H ] 3− + H 2 O → III → H 2 +[ Mo 2 ( OH ) 2 Cl 2 ] 2+ +6 Cl − ] + H + is discussed.