A tetranuclear oxofluorovanadium(IV) cluster encapsulating a Na(H 2 O) n + subunit

Hydrothermal reactions of sodium vanadate, methylenediphosphonic acid, hydrogen fluoride and the appropriate organoamine yielded the vanadium(IV)-oxyfluoride compounds [NH3(CH2)2(NH2)(CH2)2NH3]3[{Na(H2O)}⊂{V4O4F2(O3PCH2PO3)4}]·8H2O (1·8H2O) and [NH3(CH2)2(NH2)(CH2)2(NH2)(CH2)NH3]2[{Na(H2O)}⊂{V4HO4F2(O3PCH2PO3)4}]·7H2O (2·7H2O). The vanadium-oxyfluoride cationic unit {V4O4F2(O3PCH2PO3)4}10− of the compounds consists of pairs of fluoride bridged {VFO5} octahedra linked through η4-diphosphonate ligands into a three polyhedra thick band. The {Na(H2O)n}+ groups occupy the interior of the band but are displaced from the centroid toward one face so as to project the aqua ligands into the extra-annular domain. The fluoride ligands bridge two vanadium sites as well as coordinating to the sodium cation.