Tungstorhenate Heteropolyanions. 2. Synthesis and Characterization of Enneatungstorhenates(V), -(VI), and -(VII).
The tungstorhenate(V) heteropolyanion [W(9)ReO(32)](5)(-) has been isolated as guanidinium and cesium salts from reaction of [ReO(2)(PPh(3))(py)(3)](+) with sodium tungstate. Crystallographic analysis of black Cs(5)[W(9)ReO(32)].3H(2)O [triclinic, P1 or P&onemacr;; a = 10.194(1), b = 11.503(2), c = 9.682(1) Å; alpha = 100.55(1), beta = 115.81(1), gamma = 99.13(1) degrees; Z = 1], based on 3743 reflections, shows the anion to be isostructural with decatungstate, [W(10)O(32)](4)(-). Refinement in P&onemacr; led to reliability indices R = 0.084, R(w) = 0.046. Electrochemical investigation revealed the existence of Re(VI) and Re(VII) analogues, which were hydrolytically unstable in aqueous solution but which were isolated as crystalline tetra-n-butylammonium and tetra-n-heptylammonium salts, respectively, from nonaqueous solvents. The tetra-n-butylammonium salts of [W(9)Re(VI)O(32)](4)(-) and [W(10)O(32)](4)(-) were shown to be isomorphous by X-ray powder diffraction. Simulation of the Q-band ESR spectrum of [W(9)Re(VI)O(32)](4)(-) (polycrystalline solid solution in [W(10)O(32)](4)(-)) gave g(x)() = 1.69(1), g(y)() = 1.66(1), g(z)() = 1.730(2) and 10(4)A(x)()((185,187)Re, I = (5)/(2)) = (-)252(10), 10(4)A(y)() = (-)398(10), 10(4)A(z)() = (-)653(5) cm(-)(1). The orthorhombic ESR spectrum proves that the Re atom occupies one of the eight equivalent "equatorial" sites in the decatungstate structure.
Ortéga
Fernando
F
Department of Chemistry, Georgetown University, Washington, D.C. 20057.
Pope
Michael T.
MT
Evans
Howard T.
HT