Synthesis and Characterization of a Soluble Vanadium‐Containing Keggin Polyoxoniobate by ESI‐MS and 51 V NMR: (TMA) 9 [V 3 Nb 12 O 42 ]·18H 2 O

The vanadium‐containing heteropolyoxoniobate (TMA) 9 [V 3 Nb 12 O 42 ] · 18H 2 O was synthesised by hydrothermal reaction of V 2 O 5 and hydrous niobium oxide in tetramethylammonium hydroxide solution. The cluster has an α‐Keggin structure with a central VO 4 and two trans ‐bicapped VO 5 . The water‐soluble product was characterised by X‐ray crystallography, ESI‐MS and both liquid‐ and solid‐state 51 V NMR spectroscopy. The solid‐ and solution‐phase 51 V NMR spectra indicate two major peaks corresponding to one VO 4 and two VO 5 sites.