Iron-iridium mixed-metal carbonyl clusters: A Mossbauer study of the structure and of the adsorption of [Fe(2)Ir(2)(CO)(12)](2-) on MgO

(193)Ir and (57)Fe Mossbauer spectroscopy was used to investigate the structure of the [Fe(2)Ir(2)(CO)(12)](2-) cluster compound and the adsorption of this cluster on hydrated MgO. Supported samples were prepared by impregnation of the magnesia with solutions of [Et(4)N](2)[F(e)Ir(2)(CO)(12)] in acetone. The Mossbauer and FT-IR spectra of the MgO-supported cluster confirm that the bimetallic carbonyl is molecularly physisorbed onto MgO without undergoing any transformation or decomposition. The easy solvent extraction of the intact cluster from the oxide surface excludes ion pairing between the cluster anion and the Mg(2+) surface sites. Mossbauer spectra are in agreement with the refined structure of the molecular cluster and the temperature dependence of the (57)Fe Mossbauer spectra above 80 K is consistent with the low degree of interaction of the cluster with the support. This technique, therefore, appears to be promising in order to infer structural information when X-ray determination fails.