Polynuclear chromium(III) carboxlylates Part 2. Chromium(III) acetate - what's in it?

Chromium(III) acetate has been widely used in industry for decades. The com mercial material is an ill-defined substance, which represents a large numb er of compounds having different compositions, physical properties and appe arances. Several samples of Cr(III) acetate, from various commercial source s were examined by ion-exchange chromatography. All the samples were found to contain several species such as [Cr3O(O2CCH3)(6)(H2O)(3)](+) and other p ositively charged purple complexes. They also contain various amounts of th e neutral violet complex [Cr-8(OH)(8)(O2CCH3)(16)] (1) which crystallizes u pon slow evaporation of its aqueous solution. 1 is a cyclic octanuclear com plex with hydroxo and acetate ligands bridging the adjacent Cr(III) ions. T he structure of a well-defined Cr(III) acetate, namely, [Cr(H2O)(6)](O2CCH3 )(3) (2) has been determined crystallographically and its decomposition pro ducts were examined by ion-exchange chromatography. Compound 2 decomposes u nder ambient conditions, releasing acetic acid and water producing neutral and charged polynuclear Cr(III) complexes. (C) 2001 Elsevier Science BN. Al l rights reserved.