Daisy Bayot

Water-soluble niobium peroxo-complexes as precursors for the preparation of Nb-based oxide catalysts

In the frame of research aimed at developing new synthetic procedures of multimetallic Nb-based catalysts, peroxo complexes of niobium(V) of general formula A I 3 [Nb(O 2 ) 4 ] and A I 3 [Nb(O 2 ) x (H y L)]. n H 2 O (A I : NH 4 +, CN 3 H 6 + (gu); L: oxalate, tartrate, citrate) have been prepared and characterized on the basis of elemental and thermal analysis, FTIR and 13 C-NMR spectra. The crystal structure of (gu) 3 [Nb(O 2 ) 4 ] and (gu) 3 [Nb(O 2 ) 2 (C 2 O 4 ) 2 ].2H 2 O have been determined. The application of the obtained Nb complexes as precursors for the preparation of silica-supported Nb-Mo-O catalysts has been demonstrated. Combining Nb peroxo-carboxylato compounds with analogous Mo(VI) compounds in a silica-impregnation method carried out in aqueous medium leads to the formation of the supported Nb 2 Mo 3 O 14 phase.

Crystal structure of trimethylbenzylammonium hexachloroniobate(V), [(CH3)(3)C7H7N][NbCl6]

C10H16Cl6Nb, orthorhombic, Pbcm (no. 57), a = 8.246(3) A, b = 13.104(5) A, c = 16.142(7) A, V = 1744.2 A(3), Z = 4, R-gt(F) = 0.073, wR(ref)(F-2) = 0.307, T = 293 K.

Crystal structure of ammonium oxo(peroxo)(pyridine-2,6-dicarboxylato-N,O,O)aquavanadate(V), (NH4)[VO(O-2)(H2O)(C7H3NO4)]

C7H9N2O8V, orthorhombic, Pcca (No. 54), a = 13.575(4) Angstrom, b = 20.603(6) Angstrom, c = 8.026(3) Angstrom, V = 2244.8 Angstrom(3), Z = 8, R-gt(F) = 0.046, wR(ref)(F-2) = 0.155, T = 293 K.

Crystal structure of tetraguanidinium dioxo-tetraperoxo-mu-tartrato-dimolybdate(VI) dihydrate, (CN3H6)(4)[Mo2O2(O-2)(4)(C4H2O6)]center dot 2H(2)O

C16H60Mo4N24O36, orthorhombic, Pna2(1) (No. 33), a = 29.387(9) Angstrom, b = 9.979(3) Angstrom, c = 19.062(5) Angstrom, V = 5590.0 Angstrom(3), Z = 4, R-gt(F) = 0.094, wR(ref)(F-2) = 0.264, T = 293 K.