A New Class of Functionalized Polyoxometalates: Synthetic, Structural, Spectroscopic, and Electrochemical Studies of Organoimido Derivatives of [Mo₆O₁₉]^2-

A convenient method for the systematic introduction of a variety of organoimido ligands at terminal oxo sites in the hexamolybdate cluster [Bu4N]2[Mo6O19] is described, consisting of reaction with the appropriate organic isocyanate RNCO (R = n-butyl, cyclohexyl, 2,6-diisopropylphenyl) in pyridine solution. Singly functionalized imido-hexamolybdates [Mo6O18(NR)]2- incorporating each of the above substituents are described. In the case of the 2,6-(diisopropyl)phenylimido ligand (NAr), multiple functionalization has also been achieved: hexamolybdate derivatives [Mo6O(19-x)(NAr)x]2- incorporating two, three, four, and five NAr ligands at terminal sites have been prepared. The complexes have been characterized by cyclic voltammetry, multinuclear (1H, 14N, 17O, and 95Mo) NMR and electronic spectroscopy, and single-crystal X-ray diffraction studies.