Diosmium carbonyl sawhorse complexes containing a ferrocenedicarboxylato ligand

In an attempt to prepare a supramolecular assembly consisting of two, three, or four diosmium carbonyl sawhorse units linked together by dicarboxylato ligands, the reaction of [Os3(CO)12] with ferrocene-1,1′-dicarboxylic acid, Fe(C5H4COOH)2, was carried out with microwave heating. Instead of an assembly, the lone diosmium product was the single sawhorse complex [Os2(μ-ferrocene-1,1′-dicarboxylato)(CO)6] (1) with a tetradentate doubly bridging Fe(C5H4CO2–)2 ligand, a metal–metal single bond, four equatorial carbonyl ligands, and two axial carbonyl ligands. Two additional sawhorse complexes, [Os2(μ-ferrocene-1,1′-dicarboxylato)(CO)4(tri-p-tolylphosphine)2] (2) and [Os2(μ-ferrocene-1,1′-dicarboxylato)(CO)4(N,N-dimethylaminomethylferrocene)2] (3), were prepared by substituting the axial CO ligands in 1 with P- or N-donor ligands, respectively. Clusters 1, 2, and 3 represent the first examples of carbonyl sawhorse complexes with ferrocenedicarboxylato ligands, and all three were characterized with single-crystal X-ray diffraction studies.