Synthesis, Structure and Isomerism of the [Fe3Pt(μ4-Q)(CO)9(dppm)] Clusters (Q = Se, Te; dppm = Ph2PCH2PPh2)

Abstract

The reaction of K2[Fe3(μ3-Q)(CO)9] (Q = Se (K2[1a]), Te (K2[1b])) with [(dppm)PtCl2] leads to the addition of a [(dppm)Pt]2+ unit to a Fe2Q face of the initial cluster. By this way new heteronuclear clusters [Fe3Pt(μ3-Q)(CO)9(dppm)] were obtained possessing a butterfly-shaped cluster core bridged by a μ4-Q unit. It has been found that the resulting Fe-Pt clusters exist as equilibrium mixtures of two isomeric forms in solution differing by the dppm coordination mode: as a chelate ligand coordinated to Pt or as a bridging ligand coordinated to Pt and Fe atoms. The mixtures of isomers can be separated by chromatography and the pure isomers can be isolated as stable crystalline phases. Solutions of both isomers attain equilibrium at normal conditions in about 1 month as found by NMR.