Fac and mer dppe-substituted Fischer carbene complexes of chromium: X-ray, DFT and electrochemical study

X-ray crystallography data, DFT calculations and cyclic voltammograms in synergy shed light on the mer ↔ fac isomerization process of Cr carbenes of the type [(CO)3(dppe)Crdouble bond; length as m-dashC(X)R] with R = 2-thienyl or 2-furyl and X = OEt or NHCy, both in the neutral and oxidized states. Cyclohexylamino-containing complexes are easier oxidized and reduced than ethoxy-containing complexes. Dppe-containing complexes are considerably easier oxidized and reduced than non-phosphine containing Cr–Fischer carbene complexes of the type [(CO)5Crdouble bond; length as m-dashC(X)R] with X = OEt, NHBu, NMe2 or N(CH2Ph)2 and R = phenyl, thienyl, furyl, NMe-pyrrole, H or Me. The oxidation and reduction potential of the [(CO)3(dppe)Crdouble bond; length as m-dashC(X)R] complexes are not very sensitive to the influence of the heteroarene rings 2-thienyl or 2-furyl.