Spectroscopic study of the structures of [M₂(η-C₅H₅)₂(CO)_n(CNR)_4-n] complexes (n= 1 or 2; M = Fe or Ru) in solution. The structure of cis-[(η-C₅H₅)(OC)Fe(μ-CO)(μ-CNPrⁱ)Fe(CNPrⁱ)(η-C₅H₅)] in the solid state

Abstract

Various [M₂(η-C₅H₅)₂(CO)_n(CNR)_4-n] complexes have been prepared [n= 2, M = Fe, R = Ph, p-ClC₆H₄CH₂, PhCH₂, p-MeC₆H₄CH₂, p-MeOC₆H₄CH₂, D(+)-Ph(Me) CH, Me, Et, Prⁿ, Buⁿ, Pr^l, C₆H₁₁, or Bu^t; M = Ru, R = Prⁱ; n= 1, M = Fe, R = Me, Et, or Prⁱ]. In solution, they exist as rapidly interconverting equilibrium mixtures of isomers; where n= 2, the RNC ligands are less likely to adopt bridged as opposed to terminal co-ordination as R is varied along the above series. The isomer distribution is a consequence of electron-withdrawing R favouring μ-CNR co-ordination and, less importantly, the more bulky R favouring terminal CNR. Where n= 1, only one predominant isomer is observed in solution. The crystal and molecular structure of cis-[Fe₂(η-C₅H₅)₂(CO_t)-(CNR_t)(CO_μ)(CNR_μ)](R = Prⁱ) has been determined by an X-ray diffraction study. It has been solved by the heavy-atom method from photographic data and refined by full-matrix least squares to R= 0.103 for 807 non-zero unique reflections. Crystals are monoclinic with space group P2₁/c(no. 14), Z= 4, a=13.881 ± 0.015, b= 10.755 ± 0.010, c= 15.262 ± 0.015 Å, and β= 112.5 ± 0.1°.