Cation effects on imidization of the hexamolybdate dianion via direct dehydration using the green combination of dimethoxypropane in dimethylsulfoxide

The imidization of hexamolybdate clusters with aromatic amines to produce hybrid organic-inorganic molecules is a rapidly expanding area of inorganic chemistry research due to the unique combination of structural and electronic properties. The earliest methods relied on the use of highly toxic isocyanates, while more recent developments have resulted following the discovery that dicyclohexylcarbodiimide (DCC) could be used as a dehydrating agent in acetonitrile under relative mild conditions. Unfortunately, DCC remains acutely toxic, and a new alternative system is reported here, with 2,2-dimethoxypropane (DMP) serving as the dehydrating agent in dimethylsulfoxide (DMSO). To outline the utility of this new approach, a study the kinetic effects of the quaternary ammonium counter-cation size on the rate and extent of imidization is presented. Overall, in the range from the tetraethyl- to the tetraheptyl-ammonium cations, the fastest and highest conversion rates are found with the bis(tetrabutylammonium) hexamolybdate.