Chromium(II) chemistry. Part X. The preparation and properties of some ammines

Abstract

The first series of chromium(II) ammines has been isolated: [Cr(NH₃)₆]X₂ and [Cr(NH₃)₅]X₂(X = Cl, Br, or I); CrX₂(NH₃)₂(X = Cl or Br); [Cr(NH₃)₄(OH₂)][SO₄]; and Cr(NH₃)₂(SO₄). The hexa-ammines, obtained by bubbling ammonia through ethanolic solutions of the chromium(II) halides, lose ammonia readily and reversibly to form penta-ammines. Thermal decomposition of the latter gives the diammine halides. The sulphates have been obtained by similar procedures. From magnetic, spectroscopic, and X-ray powder investigations, the hexa-ammines and penta-amines have been assigned tetragonal octahedral and square-pyramidal structures respectively, and the diammines anion-bridged six-co-ordinate structures. The tetra-ammine sulphate is square pyramidal with co-ordinated water.