The formation and molecular structure of (η⁵-nitrocyclopentadienyl)dicarbonylrhodium

A reaction between sodium or lithium nitrocyclopentadienide and dichlorotetracarbonyldirhodium produces (η⁵-nitrocyclopendtadienyl)dicarbonylrhodium in 22–30% yield, the first η-nitrocyclopentadienyl-transition metal compound to be synthesized directly from nitrocyclopentadienide anion. The product has been characterized by spectroscopic and by X-ray diffraction techniques, the latter representing the first such structural determination for a nitrocyclopentadienylmetal compound. Red crystals of the title compound are triclinic, P?, with a  6.247(4), b  6.484(4), c  11.311(6) Å, α  76.79(5), β  79.40(5), γ  72.95(5)°, and D_c  2.12 g cm^-3 for Z  2. Least-squares refinement gave a final conventional R value of 0.056 for 1438 independent observed reflections. The nitrocyclopentadienyl ligand is significantly nonplanar.