Synthesis and Characterization of [(OH)TeNb5O18](6-) in Water Solution, Comparison with [Nb6O19](8-)

• Published in: Inorganic chemistry Vol. 55; no. 4; pp. 1381 - 1389
• Main Authors: Abramov, Pavel A, Zemerova, Tatiana P, Moroz, Nikolay K, Kompankov, Nikolay B, Zhdanov, Artem A, Tsygankova, Alfiya R, Vicent, Cristian, Sokolov, Maxim N
• Format: Journal Article
• Language: English
• Published: United States 15-02-2016
• ISSN: 1520-510X
• DOI: 10.1021/acs.inorgchem.5b01806

Reaction of [Nb6O19](8-) with H6TeO6 in water gives telluropentaniobate [(OH)TeNb5O18](6-) (1) as single product, which was isolated as Na(+) and mixed Na(+)/K(+) salts. Crystal structures were determined for Na6[(OH)TeNb5O18]·15H2O (Na6-1) and K6Na[Nb(5.5){Te(OH)}(0.5)O(18.5)]·26H2O (K6Na-1). Formation of 1 was monitored with electrospray ionization mass spectrometry (ESI-MS) and (125)Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)TeNb5O18](6-) and [Nb6O19](8-) in borate buffer. No condensation or degradation products were detected. Reactions of 1 with {Cp*Rh}(2+) sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by (125)Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}(2+) to different {M3O3} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na3[{Cp*Rh}2TeNb5O19]·24H2O (Cp*2Rh2-1) with two {Cp*Rh}(2+) fragments capping the opposing faces of the Lindqvist anion.