Preparation and characterisation of some new Mo/O/XR (X = P or As) heteropoly blue complexes

A new series of molybdenum organophosphonates with a Mo∶P ratio of 1∶1 have been isolated. The proposed formulation for these compounds is (Mo^V₂Mo^VI₄O₁₂)(O₃XR)₄[O₂(OH)XR]₂(EtOH)_x [when X = P, R = C₆H₅, C₆H₅CH₂, CH₃ or C₂H₅; when X = As, R = C₆H₅; x = 5 (for R = C₆H₅ or CH₂C₆H₅) or 4 (for R = CH₃ or C₂H₅)]. These compounds are intensely blue in colour, as expected for compounds of the heteropoly blue category. XPS data indicate a Mo(v)∶Mo(vi) ratio of 1∶2 in these compounds, and the FTIR, solid-state and solution NMR, TGA, UV/Vis, magnetic and electrochemical data are consistent with the proposed formulations.