Potentiometric study of the molybdenum(VI)–benzilic acid system. Structural characterisation and electrochemical properties of [NH4]2[MoO2{O2CC(O)Ph2}2]·2H2O

The formation of complexes between molybdate and benzilate (2-hydroxy-2,2-diphenylacetate), Hbza–, ions has been investigated in the range pH 2–7 by potentiometric measurements. Computer treatment of the potentiometric data revealed the formation of two complexes the [MoO4]2–, Hbza–, H+ stoichiometries of which are [1,2,2] and [2,2,4]; log β122= 17.35, log β224= 29.07. Compared to other less bulky hydroxycarboxylate ligands previously studied, this result indicates that the phenyl groups of benzilate only prevent the formation of [2,2,5] dimeric complex which presumably has a double oxo bridge. The mononuclear [1,2,2] complex has been isolated and its structure determined by X-ray analysis of its ammonium salt, [NH4]2[MoO2{O2CC(O)Ph2}2]·2H2O; monoclinic, space group P21/n, a= 8.106(2), b= 25.702(8), c= 13.628(4)A, β= 90.62(2)° and Z= 4. The redox properties of this complex salt were also investigated and compared with those previously found for an analogous complex containing two thiobenzilate ligands.

[1]  F. A. Schultz,et al.  Effect of substituting sulfur for oxygen on the heterogeneous electron transfer kinetics of oxomolybdenum(V) hydrotris (3,5-dimethyl-1-pyrazolyl)borate complexes , 1994 .

[2]  F. Vicente,et al.  Molybdenum complexes with sterically-hindered thio-carboxylate ligands. Electrochemical properties of the anionic complex bis(2, 2-diphenyl-2-mercaptoethanoate)dioxomolybdate(VI) in protic solvents , 1994 .

[3]  J. J. Cruywagen,et al.  Molybdenum(VI) complex formation. Part 7. Equilibria and thermodynamic quantities for the reactions with nitrilotriacetate , 1994 .

[4]  M. J. Scott,et al.  Molybdenum-mediated oxygen-atom transfer: an improved analog reaction system of the molybdenum oxotransferases , 1993 .

[5]  J. J. Cruywagen,et al.  Molybdenum(VI) and tungsten(VI) complex formation. Part 5. The reaction with lactate in 1.0 mol dm–3 sodium chloride medium , 1993 .

[6]  Andrew J. P. White,et al.  Salicylato (sal) complexes of second- and third-row transition elements, and the crystal structure of [NMe4]2[MoO2(sal)2]·2H2O , 1993 .

[7]  F. Vicente,et al.  Voltammetric behaviour of monomeric fac-trioxomolybdenum(VI) complexes with aminocarboxylic ligands in aqueous media , 1992 .

[8]  E. Garcı́a-España,et al.  Compounds of molybdenum(VI) with aspartic acid: A spectrophotometric and potentiometric study of the formation and interconversion equilibria in aqueous solution , 1990 .

[9]  P. Gómez‐Romero,et al.  Model compounds for the active sites of oxo-transfer molybdoenzymes. Synthesis, structural characterization, and electrochemical properties of [NH4]2[MoO2{O2CC(S)Ph2}2] , 1990 .

[10]  A. Bianchi,et al.  Low-spin six-co-ordinate cobalt(II) complexes. A solution study of tris(violurato)cobaltate(II) ions , 1988 .

[11]  L. Nassimbeni,et al.  Complexation between molybdenum(VI) and oxalate: Crystal and molecular structure of [(−)Co(en)3][MoO3(C2O4)OH2]I·2 H2O , 1987 .

[12]  J. Ramírez,et al.  Compounds of tungsten(VI) with citric acid: A spectrophotometric, polarimetric and hydrogen-1, carbon-13 N.M.R. study of the formation and interconversion equilibria in aqueous solution , 1986 .

[13]  W. Robinson,et al.  The crystal structure of a Di(tetramethylammonium)-bis[R,R-tartrato(2-)]-cis-dioxomolybdate(VI), (NMe4)2[MoO2(C4H4O6)2] · EtOH · 1.5 H2O, with comments on tartrate coordination , 1986 .

[14]  J. Ramírez,et al.  Tungsten-mannitol and sorbitol complexes: Structural characterization by IR and carbon-13 nuclear magnetic resonance spectroscopy , 1986 .

[15]  J. Belenguer,et al.  Tungsten(VI) complexes formed in an excess of gluconic acid: A polarimetric and spectrophotometric study , 1985 .

[16]  K. Tytko,et al.  Equilibrium studies of aqueous polymolybdate solutions in 1 M sodium chloride medium at 25.degree.C , 1985 .

[17]  J. Ramírez,et al.  Compounds of W(VI) with l(−)malic acid: a polarimetric and 1H nuclear magnetic resonance study of the formation and interconversion equilibria in excess of W(VI) , 1985 .

[18]  P. Gans,et al.  SUPERQUAD: an improved general program for computation of formation constants from potentiometric data , 1985 .

[19]  T. Halbert,et al.  Ligand and induced internal electron transfer pathways to new Mo–S and W–S dithiocarbamate complexes , 1985 .

[20]  F. Caturla,et al.  Complexes of molybdenum(VI) with organic diacid ligands: The molybdenum(VI)-malonic acid system , 1983 .

[21]  C. Knobler,et al.  Molybdenum(VI) complexes with malic acid: their inter-relationships, and the crystal structure of dicaesium bis[(S)-malato(2–)]-cis-dioxomolybdate(VI)–water (1/1) , 1983 .

[22]  C. N. Reilley,et al.  Carbon-13, oxygen-17 and molybdenum-95 nuclear magnetic resonance studies of oxomolybdenum(VI) complexes , 1982 .

[23]  A. Beltrán,et al.  Study of the complexes of Mo(VI) with malic acid , 1981 .

[24]  F. Caturla,et al.  Mo(VI) oxalate complexes , 1981 .

[25]  F. A. Schultz,et al.  Di-.mu.-oxo, .mu.-oxo-.mu.-sulfido, and di-.mu.-sulfido complexes of molybdenum(V) with EDTA, cysteine, and cysteine ester ligands. Preparation and electrochemical and spectral properties , 1977 .

[26]  G. C. Allen,et al.  Electronic spectra of the hexafluorometalate(III) complexes of the first transition series , 1971 .