TUNGSTEN(VI) COMPLEXES WITH CITRIC-ACID (H4CIT) - STRUCTURAL CHARACTERIZATION OF NA6[(WO2(CIT))2O].10H2O

被引:36
作者
LLOPIS, E [1 ]
RAMIREZ, JA [1 ]
DOMENECH, A [1 ]
CERVILLA, A [1 ]
机构
[1] UNIV VALENCIA,DEPT QUIM INORGAN,DR MOLINER 50,I-46100 BURJASSOT,ITALY
来源
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS | 1993年 / 07期
关键词
D O I
10.1039/dt9930001121
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
The complex anion [W2O5(cit)2]6- was obtained by crystallisation from an equimolar aqueous solution of sodium tungstate and citric acid (H-4cit). It has been characterised by elemental analysis, IR and H-1 and C-13 NMR spectroscopy. The IR spectrum is consistent with a monooxo-bridged dinuclear structure as revealed by a single-crystal X-ray diffraction study of Na6[W2O5(cit)2].10H2O. The crystals are monoclinic, space group P2(1)/a, a = 17.708(3), b = 9.908(2) and c = 9.018(2) angstrom, beta = 91.57(2)-degrees, R = 0.025 for 3101 observed [l/sigma(l) greater-than-or-equal-to 2.5] reflections. The complex anion contains a O2WOWO2 core with the bridging oxo group lying at a crystallographic centre of symmetry (W-O(b)-W 180-degrees). Each citrate ligand is three coordinated to one tungsten atom through the deprotonated hydroxy, alpha-carboxylate, and one beta-carboxylate group. Principal dimensions are: W-O(b) 1.893(1), (W=O(t))av 1.757(2), W-O(hydroxy) 1.958(2), W-O(alpha-carboxy) 2.195(3) and W-O(beta-carboxy) 2.289(2) angstrom. All methylene and beta-carboxylate groups become magnetically equivalent upon redissolution in water as a result of the dissociation of the less strongly bonded beta-carboxylate group.
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页码:1121 / 1124
页数:4
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