Mixed cobalt–nickel oxydiacetate [CoxNi1−x(oda)(H2O)3] · 1.5H2O compounds (; x = 0.3, 0.4, 0.6) were synthesized from the reaction of aqueous solutions of a mixture of nickel dichloride and cobalt dichloride with a 1:1 mixture of Na2CO3 and oxydiacetic acid, O(CH2COOH)2. In particular, compound [Co0.4Ni0.6(oda)(H2O)3] · 1.5H2O (1) was characterized by single-crystal X-ray analysis. Complex 1 is a co-crystallization of [Ni(oda)(H2O)3] · 1.5H2O and [Co(oda)(H2O)3] · 1.5H2O compounds, the latter species being a new hydrated form of cobalt oxydiacetate that shows a fac-coordination for the oda ligand. These compounds can be used for the preparation of mixed metal oxides. For instance, thermal decomposition of 1, carried out under a nitrogen atmosphere, produces essentially Co0.4Ni0.6O oxide.

This work was supported by the Spanish Ministerio de Educación y Ciencia (BQU2001-3715 and CTQ2004-0084) and Junta de Andalucía. We are grateful to Raquel Moyano for the preparation of some samples.

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