Three new staphylonuclear chloromolybdates : K₆Mo₃Cl₁₂, (NH₄)₇Mo₃Cl₁₃,H₂O, and Cs₆Mo₄Cl₁₆

Abstract

The new compounds, K₆Mo₃^IICl₁₂; (NH₄)₇Mo₃^IICl₁₃.H₂O; and Cs₆Mo₄Cl₁₆ (containing molybdenum in oxidation state +2.5) have been precipitated by the appropriate cation from solutions of molybdenum(II) acetate in 12M hydrochloric acid. The absorption spectra of potassium and ammonium salts are similar in the solid state and solution. Since the compounds are strong reducing agents and short-lived in solution, their formulation as a staphylonuclear (i.e. metal-clustered) trimer or tetramer rests on their diamagnetism, stoicheiometry, and spectral similarities. It is proposed that the chloromolybdates adopt entirely novel, compact polymers by stacking the chlorine atoms into "close packed" layers. The Mo₃Cl₁₃ group consists of two layers of chlorine atoms (seven and six) generating three octahedral locations for the molybdenum atoms at the corners of a regular triangle. The Mo₃Cl₁₂ group is similar but deficient in one chlorine atom. The Mo₄Cl₁₆ group is related to Mo₃Cl₁₃ and consists of three layers of chlorine atoms (seven, six, and three) providing four octahedral locations for the molybdenum atoms at the corners of a tetrahedron.