Synthesis and supramolecular structures of iso- and heteropolymetallates assisted by organoamino phosphonium cations

Polyoxometallate (POM) clusters represent an interesting choice of building blocks for the construction of inorganic-organic hybrid materials. The supramolecular aggregation of several iso- and heteropolymetallate anions in presence of various organoamino phosphonium cations is described. The phosphonium POM salts 4-8 were prepared by the reaction of [P(NHR)₄]Cl {1 (R = cyclohexyl), 2 (R = iso-butyl) and 3 (R = iso-propyl)} with Na₂MoO₄·2H₂O/Na₂WO₄·2H₂O. The compound 9, [P(NHCy)₄]₃[AsMo₁₂O₄₀], was prepared in a three component reaction involving 1, Na₂MoO₄·2H₂O and Na₂HAsO₄. Formation of the Keggin clusters in 7 and 8 was achieved by a facile P-N bond cleavage of 3 under the acidic conditions of the reaction. X-ray structure analyses of the title compounds show an interesting range of hydrogen bonded supramolecular structures with topologies resembling from 2D-sheets to 3D-networks.