Nouveaux complexes du rhodium(III): Le di-μ-acetato-bis[(aquo)-acetato-hydroxo-aminej-dirhodium(III): [Rh 111(OAc)(HOH…OAc)(OH)(NH 3)] 02 préparation, identification, étude de quelques unes de ses propriétés

Abstract

Hot acetic acid reacts with the rhodium(III)-trihydroxo-diaquo-monoa-mine [Rh 111(OH) 3(H 2O) 2(NH 3)] 0 forming the new compound: [Rh 111(OAc)(HOH… OAc)(OH)(NH 3)] 0 2, di-μ-acetato-bis[(aquo)-acetato-hydroxo-amine]-dirhodium(III) in a quantitative yield. When a large excess of acetic acid is used, the respective addition product is obtained: [Rh III(OAc)(HOH…OAc)(OH)(NH 3)] 2, AcOH. Chemical and spectrophotometric studies (infra-red, visible and ultra-violet) and nuclear magnetic resonance data permit us to assign a dimeric structure, wherein the rhodium is trivalent. The complex described is soluble in water as well as in several common organic solvents (alcohol, acetic acid, dimethylsulfoxide, acetonitrile). Although the complex is stable in neutral solutions, in the presence of free acetic acid, in an aqueous solution, it hydrolyses easily, partially exchanging the acetato groups by hydroxo groups; in an alcoholic solution, the rhodium(III) is reduced to an acetato-aquo-amino complex of divalent rhodium. The product starts decomposing in an inert atmosphere at about 70 °C, leading to metallic rhodium at about 300 °C.