Molecular structure and bond characterization of the fischer-type chromium - Carbene complexes (CO)₅Cr=C(X)R (X = H, OH, OCH₃, NH₂, NHCH₃ and R = H, CH₃, CH=CH₂, Ph, C≡CH)

In this work we have examined a series of 25 different Fischer carbene complexes of the type (CO)₅Cr=C(X)R with X = H, OH, OCH₃, NH₂, and NHCH₃ and R = H, CH₃, CH=CH₂, Ph, and C≡CH, to analyze the influence of each substituent on the molecular structure and bonding of these complexes. Energy and charge decomposition analysis of the interaction between the chromium pentacarbonyl and the carbene fragments reveal that for the metal - carbene bond donation is quantitatively more important than back-donation. However, it is the back-donation rather than donation that correlates with most geometrical and electronic parameters of the complexes studied. The reasons for the larger influence of back-donation on the molecular structure of Fischer carbene complexes are discussed.