Polyoxomolybdates Functionalized with Phosphonocarboxylates

The novel, functionalized heteropolymolybdate [(O2CCH2PO3)2Mo5O15]6- (1) has been synthesized and characterized by IR and 31P NMR spectroscopy and elemental analysis. Single-crystal X-ray analysis was carried out on Rb4KNa[(O2CCH2PO3)2Mo5O15]·H2O, which crystallizes in the monoclinic system, space group P21/n, with a = 10.146(2) Å, b = 13.704(3) Å, c = 20.577(4) Å, β = 94.88(3)°, and Z = 4. The title polyanion consists of a ring of five MoO6 octahedra with four edge junctions and one corner junction. This nonplanar arrangement is stabilized by two phosphonocarboxylate groups that are bound via their phosphonate functionalities on opposite sides of the ring. As a result the two dangling arms with their terminal carboxylate groups protrude away from the molybdenum−oxo framework in diametrically opposed directions. The solid-state structure of 1 is preserved in solution on the basis of NMR. We also report on the synthesis and characterization of the isostructural derivative [(O2CC2H4PO3)2Mo5O15]6- (2).