Convenient synthesis and Raman spectral characterization of diammonium monomolybdate(VI)

Abstract

A convenient and cost-effective method is reported for the preparation of gram quantities of an ammonium-rich Mo compound viz. diammonium monomolybdate(VI) (NH₄)₂MoO₄ (1). The process involves a thorough grinding of a commercial sample of ammonium heptamolybdate tetrahydrate (NH₄)₆[Mo₇O₂₄]·4H₂O with an excess of ammonium bicarbonate followed by thermal treatment. The facile formation of (1) is confirmed by its characteristic Raman spectrum. The use of Raman spectroscopy to distinguish between tetrahedral monomolybdate(VI) and heptamolybdate, dichromate and monochromate(VI), paratungstate and monotungstate(VI) as well as the identification of the species present in ammoniacal solutions of MO₃ (M = Cr, Mo, W) are reported.