[ε-PMo12O36(OH)4{La(H2O)4}4]5:: The first ε-PMo12O40 Keggin ion and its association with the two-electron-reduced α-PMo12O40 isomer

Six Mo dimers arranged around a central PO4 tetrahedron form the core of the novel ε-Keggin polyoxocation [ε-PMo12O36(OH)4{La(H2 O)4}4]5+ (see structure) capped with four {La(H2O)4}3+ units. A 31P NMR spectroscopy study shows that the ε-Keggin ion is unstable in aqueous solution, and leads to the formation of a polyanion/polycation salt, which is crystallographically characterized.