Publications

Cupric siliconiobate. Synthesis and solid-state studies of a pseudosandwich-type heteropolyanion

Anderson, Travis M.; Alam, Todd M.; Rodriguez, Marko A.; Bixler, Joel N.; Xu, Wenqian; Parise, John B.; Nyman, M.

The Na+ and [Cu(en)2(H2O) 2]2+ (en = ethylenediamine) salt of a pseudosandwich-type heteropolyniobate forms upon prolonged heating of Cu(NO3)2 and hydrated Na14[(SiOH)2Si2Nb 16O54] in a mixed water-en solution. The structure [a = 14.992(2) Å, b = 25.426(4) Å, c = 30.046(4) Å, orthorhombic, Pnn2, R1 = 6.04%, based on 25869 unique reflections] consists of two [Na(SiOH)2Si2Nb16O54]13- units linked by six sodium cations, and this sandwich is charge-balanced by five [Cu(en)2(H2O)2]2+ complexes, seven protons, and three additional sodium atoms (all per a sandwich-type cluster). Diffuse-reflectance UV-vis indicates that there is a λmax at 383 nm for the CuII d-d transition and the 29Si MAS NMR spectrum has two peaks at -78.2 ppm (151 Hz) and -75.5 ppm (257 Hz) for the two pairs of symmetry-equivalent internal [SiO4]4- and external [SiO3(OH)]3- tetrahedra, respectively. Unlike tungsten-based sandwich-type complexes, the [Na(SiOH)2Si 2Nb16O54]13- units are linked exclusively by Na+ instead of one or more d-electron metals. © 2008 American Chemical Society.