Basic halides and related species of molybdenum(III). I. The empirical formulae and unit cell dimensions of the basic halides

Abstract

The basic halides MoOX(H₂O), (X = F, Cl) were examined by vacuogravimetric and evolved gas analysis and by X-ray and electron diffraction techniques. The basic chloride prepared by slow crystallization had y = 3.08, with an orthorhombic unit cell 0.723 by 0.820 by 1.805 nm. Basic chlorides produced by rapid precipitation were less crystalline, of slightly larger unit cell dimensions and had 3.0 < y < 4.3. The water in excess of y = 3 was loosely held, while three water molecules per molybdenum were more strongly held. The fluoride, which could not be obtained with the perfect MoOF(H₂O)₃ stoichiometry, was isomorphous (cell parameters 0.710 by 0.823 by 1.824 nm for [MoOF^0.96(OH)_0.04(H₂O)₃] (H₂O)_0.28). It is concluded that the only hydrate of MoOX existing under normal conditions is MoOX(H₂O)₃, not the previously reported tetrahydrate.