ABSTRACT
Two vanadium(V)-substituted tungsto-polyoxometalate isomers, 1- and 4-[S2VW17O62](5-), were prepared as their tetra-alkyl ammonium salts from a W(VI)-H2SO4-V(V) reaction mixture in aqueous CH3CN solution. X-ray crystallographic structural analysis revealed that both isomers have a Wells-Dawson-type structure with a higher occupancy of vanadium at polar sites and belt sites for 1- and 4-[S2VW17O62](5-), respectively. The isomers were also characterized by elemental analysis, infrared, Raman, UV-vis, and (51)V NMR spectroscopies as well as voltammetry, and the data obtained were compared with that derived from [S2W18O62](4-). Significantly, the reversible potentials for the vanadium(V/IV) couple for both 1- and 4-[S2VW17O62](5-) in CH3CN (0.1 M n-Bu4NPF6) are considerably more positive than the tungstate reduction process exhibited by the [S2W18O62](4-) framework, implying that the presence of vanadium should be useful in catalytic reactions. The one-electron-reduced [S2V(IV)W17O62](6-) forms of both isomers were prepared in solution by controlled potential bulk electrolysis and characterized by voltammetry and EPR spectroscopy.
Subject(s)
Coordination Complexes/chemistry , Tungsten Compounds/chemistry , Vanadium/chemistry , Crystallography, X-Ray , Models, MolecularABSTRACT
In the title compound, [CaCo(3)(C(4)H(5)NO(4))(3)(OH)(3)O(H(2)O)(5)]·2.54H(2)O, the Co atom is octa-hedrally coordinated by one imino-diacetate (ida) dianion as a facial O,N,O'-tridentate ligand, two µ(3)-OH groups and one µ(3)-O ligand, forming an partial Co(3)O(4) cubane cluster. This unit coordinates to a Ca(II) cation in an O,O',O''-tridentate fashion, generating a distorted CaCo(3)O(4) cubane-type cluster. The Ca-µ(3)-O distances [2.429â (5)-2.572â (6)â Å] are much longer than the Co-µ(3)-O bonds [1.895â (5)-1.941â (5)â Å]. The Ca(II) cation is also coord-inated by five water mol-ecules with Ca-O distances in the range 2.355â (6)-2.543â (6)â Å. There are three additional uncoordinated water mol-ecules in the asymmetric unit, the occupancy of which refined to 0.54â (3). In H(2)O (or D(2)O), the title complex hydrolyses to Ca(2+) (aq) cations and [Co(3)(ida)(3)(µ(2)-OH)(3)(µ(3)-O)](2-) anions.
ABSTRACT
In the title compound, [Co(C(4)H(3)N(2)S)(C(6)H(18)N(4))](Cl)PF(6), the Co(III) ion is coordinated by a tripod-like tetra-dentate ligand and a monoanionic N,S-bidentate ligand in an approximately octa-hedral CoN(4)OS geometry. The anionic S atom of the pyrimidine-2-thiol-ate (pymt) ligand is coordinated in the trans position to the primary amine N atom (Nprim) of the tris-(2-amino-ethyl)amine (tren) ligand. The crystal structure exhibits short inter-molecular N-Hâ¯N hydrogen bonds (Nâ¯N <3.2â Å), and inter-molecular N-Hâ¯Cl and C-Hâ¯F contacts, leading to the formation of an infinite two-dimensional network.
ABSTRACT
In the title compound, [Mo(C(5)H(4)NS)(3)(NO)]·2H(2)O, the Mo atom is coordinated by a nitrosyl ligand and three monoanionic N,S-bidentate ligands in a distorted MoN(4)S(3) penta-gonal-bipyramidal mol-ecular geometry. The pyridine N atom of one pyridine-2-thiol-ate (pyt) ligand is coordinated to the Mo atom in the trans position relative to the NO ligand [N(pyt)-Mo-N(NO) = 170.62â (19)°]. The compound has C(s) symmetry, with a mirror plane that includes one pyt ring and the NO group. The S-Mo-N(NO) and N(pyt)-Mo-N(NO) angles [97.24â (12) and 91.87â (8)°, respectively] are large relative to the ideal angles of 90°. In the crystal, the mol-ecules pack in a zigzag arrangement. The cavities between the mol-ecules are occupied by disordered water mol-ecules of crystallization.
