Tungstorhenate heteropolyanions. 2. Synthesis and characterization of enneatungstorhenates(V), -(VI), and -(VII)

Abstract

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, P 1 or P 1̄; a = 10.194(1), b = 11.503(2), c = 9.682(1) Å; α = 100.55(1), β = 115.81(1), γ = 99.13(1)°; Z = 1], based on 3743 reflections, shows the anion to be isostructural with decatungstate, [W 10 O 32 ] 4 - . Refinement in P 1̄ 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.