The crystal and molecular structure of bis(μ-dipenylphosphido-μ-carbonyl-π-methylcyclopentadienylcarbonyl-iron)rhodium hexafluorophosphate (2RhFe)

The structure of the title compound was determined from three-dimensional X-ray diffractometer data. The compound crystallizes in space group Pbca with Z = 8 and cell dimensions: a = 19.92 Å, b = 25.96 Å, c = 15.82 Å. The structural analysis, based on 2541 independent reflections, has converged to a final R₁ of 0.062. The structure consists of a trinuclear non-closed rhodium-iron complex with μ-diphenylphosphido and carbonyl groups bridging the rhodium and iron atoms. The RhFe distances are 2.659(2) and 2.674(1) Å. Each iron atom is additionally bonded to a methylcyclopentadienyl group and a terminal carbonyl group. The closed structure (2RhFe)(FeFe), predicted on the basis of the "18 electron rule" and observed in related molecules, is suggested as being unstable with respect to the open structure as a result of the substitution of carbonyl ligands by the highly basic μ-phosphido groups.