Preparation of nanocrystalline metal oxides and intermetallic phases by controlled thermolysis of organometallic coordination polymers

Organometallic coordination polymers of the super-Prussian blue type [(Me3Sn)(n)M(CN)(6)] (Me = CH3; n = 3, 4; M = Fe, Co, Ru) were subjected to thermolysis in different atmospheres (air, argon, hydrogen/nitrogen). In air, oxides were found: Fe2O3/SnO2 (crystalline and nanocrystalline), Co2SnO4 and RuO2. In argon and in hydrogen, the intermetallic phases FeSn2, CoSn2, Ru3Sn7 and Fe3SnC were obtained. A detailed mechanistic study was carried out using thermogravimetry (TG), X-ray diffraction (XRD), X-ray absorption spectroscopy (EXAFS) at Fe, Co, Ru and Sn K-edges, infrared spectroscopy (IR) and elemental analysis. Below 250 degrees C, Me3SnCN and (CN)(2) are released, whereas above 250 degrees C oxidation or pyrolysis leads to the corresponding oxides or intermetallic phases. Polymeric cyanides containing at least two metals have turned out to be suitable precursors to prepare well-defined oxides and intermetallic phases at comparatively low temperature. (C) 2000 Editions scientifiques et medicales Elsevier SAS. All rights reserved.