Template synthesis of {(MoV2O4)(O3PCH2PO3)}n clusters (n = 3, 4, 10): solid state and solution studies

Abstract

The influence of three exogenous ligands (acetate, formate and carbonate) on the condensation process of the [Mo₂O₄]²⁺ dioxocation with the [O₃PCH₂PO₃]⁴⁻ group has been investigated. Four cyclic or bicyclic compounds have been isolated and characterized by X-ray diffraction studies. Two closely related acetato and formato ovoidal duodecanuclear compounds, Na₂₄[Na₄(H₂O)₆{(Mo₂O₄)₁₀(O₃PCH₂PO₃)₁₀(CH₃COO)₈(H₂O)₄}]·103H₂O (1) and Na₂₈[Na₂{(Mo₂O₄)₁₀(O₃PCH₂PO₃)₁₀(HCOO)₁₀}]·110H₂O (2), respectively, have been obtained. Their structures can be described as two interconnected nonequivalent wheels, delimiting a large cavity. When the condensation is performed in similar conditions but replacing carboxylato groups by carbonato ligands, the ellipsoidal octanuclear Na₁₁[Na(H₂O)₂{(Mo₂O₄)₄(O₃PCH₂PO₃)₄(CO₃)₂}]·70H₂O (3) compound is isolated. ³¹P NMR spectroscopic studies have shown that complexes 1 and 3 are stable in solution at room temperature. Nevertheless, on heating an aqueous solution of 3, the Na₈[(Mo₂O₄)₃(O₃PCH₂PO₃)₃(MoO₄)]·18H₂O (4) complex, free of carbonato groups, is obtained. 4 is a hexanuclear Mo^V wheel encapsulating a tetrahedral [Mo^VIO₄]²⁻ anion. Its rational synthesis using a controlled Mo^V/Mo^VI ratio is also presented.