Synthesis, structure and DFT study of cymantrenyl Fischer carbene complexes of group VI and VII transition metals

•DFT calculations on configurations of trimetallic complexes.•Crystal structure of first carbene complex with cymantrenyl substituent.•Crystal structures of axial and equatorial trimetallic carbene complexes.•Calculated NBO donor–acceptor interactions show intramolecular stabilization.

Bi- and trimetallic carbene complexes of group VI and VII transition metals (Cr, Mo, W, Mn and Re), with CpMn(CO)3 as the initial synthon, have been synthesised according to the classical Fischer methodology. Crystal structures of the novel carbene complexes with general formula [Mx(CO)y-1{C(OEt)(MnCp(CO)3)}], where x = 1 then y = 3 or 6; x = 2 then y = 10, of the complexes are reported. A density functional theory (DFT) study was undertaken to determine natural bonding orbitals (NBOs) and conformational as well as isomeric aspects of the polymetallic complexes. Application of the second-order perturbation theory (SOPT) of the natural bond orbital (NBO) method revealed stabilizing interactions between the methylene C–H bonds and the carbonyl ligands of the carbene metal moiety. These stabilization interactions show a linear decrease for the group VI metal carbene complexes down the group.

Graphical abstractSynthesis, X-ray study and NBO analysis of Fischer ethoxy carbene complexes with cymantrenyl substituents.Figure optionsDownload full-size imageDownload as PowerPoint slide