A Novel Phosphovanadate of Co(III) Hexammine: Co(NH_3)_6(V_1.5P_O.5)O_6OH

摘要

The new phosphovanadate Co(NH_3)_6(V_1.5P_0.5)O_6OH has been synthesized by a hydrothermal method at 220 deg C. It crystallizes in the P2_1/c space group with a = 9.5206(8), b = 6.9631(6), c = 17.108(1), #beta# = 93.028(7), and Z = 4. The structural resolution using single-crystal X-ray diffraction leads to R(F_o) = 3.63% and R_w(F_o~2) = 10.67%. This structure consists of [Co(NH_3)_6]~(3+) cations and [V_1.5P_0.5O_6OH]~(3-) anions assembled in a distorted rock salt arrangement. The presence of the Co(III) hexammine complex [Co(NH_3)_6]~(3+) is particulary original in this sturcture since no complexes have been isolated up to now in phosphovanadates. The V_1.5P_0.5O_6OH diphosphovanadate group, wiht one vanadium tetrahedral site and one tetrahedral site statistically occupied by 0.5 vanadium and 0.5 phosphorus atom, corresponds to the random distribution of V_2O_6OH and VPO_6OH groups as confirmed by the IR spectroscopy study. Magnetic measurements show that the Co(III) cation adopts a low spin configuration.