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, Prl, C6H11, or But; 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(COt)-(CNRt)(COµ)(CNRµ)](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°.