关键词: 十五钒酸盐, 混合价钒络合物, 晶体结构

Abstract: Using VOSO₄ or VOCl₂ as the starting materials, the title complex was prepared with additive agents NH₂OH.HC1, NH₂CH₂COOHin the liquor with the final pHrange of 8-9 controlled by NaOH.The title complex crystallizes in space group D³_3h-P62m with unit cell constants a= 13. 111 (7)Å, c=11. 130(4)Å and Z=1 for chemical formula (V₁₅O₃₆Cl)(NH₄)₃Na₇-30H₂O. Those vanadium coordinates were derived by Patterson-minimum function method first and then the position parameters for the other non-hydrogen atoms were obtained by the Fourier difference techniques. Using 1084 independent reflections, the block-diagonal least-squares refinement for structural parameters gave final discrepency factor Rand R_w being<0.0353 and 0. 0344 respectively. X-ray structure analysis shows that in each unit cell two special positions with 3 symmetry are occupied by two (Na₂(H₂O)₉)²⁺ groups and one 6m2 position is occupied by a chlorion-contained pentadecavanadate anion (V₁₅O₃₆Cl)10- in which there are 15 terminal-oxygen O_a, 3 bridged-oxygen O_b, 18 triple-linked O_c and three kinds of 15 Vanadium atoms. Carefully considering all the information of chemical bond parameters, hydrogen linking as well as the calculation results of bond-valence sum for all Vand Oatoms, we recognize that three V (3) atoms are in V (Ⅳ ) valence state and the rest 12 atoms of V (Ⅰ), V(Ⅱ) in IV-Vmixed valence state. The average occupation ratio of V( Ⅴ ) for V(Ⅰ) and V(Ⅱ) is - 0. 25 which implies the pentadecavanadate group belongs to a special kind of poly-vanadate group in which the V(Ⅳ) plays the main part in holding the back-bone of the cluster and tolerates some extent V( Ⅴ) residing in.

Key words: Pentadecavanadate, Mixed valence V complex, Crystal structure