Structural and conformational study of pentacarbonyl and phosphine substituted Fischer alkoxy- and aminocarbene complexes of molybdenum

• Synthesis of penta-, tetra- and tricarbonyl Fischer Mo carbene complexes.
• DFT conformation analysis yields 2–16 conformations per complex.
• Crystal structures show conformational preference in solid state.
• Calculated NBO donor–acceptor interactions show intramolecular H-bond interactions.
• Calculated NBO donor–acceptor interactions show intermolecular H-bond interactions.

The synthesis and selected crystal structures of a series of nine (eight are reported for the first time) Mo(0) Fischer carbene complexes of the formula [(CO)3(L,L′)MoC(Y)(2-furyl)] with Y = OEt, NH2 or NHCy; L,L′ = CO,CO; PPh3,CO; dppe (1,2-bis(diphenylphosphino)ethane) are reported. DFT quantum chemical calculations on the different possible isomers and conformers of the Mo carbene complexes yielded more than one stable conformation for each complex. The small energy difference between some of the conformers of the same complex indicates that in some cases more than one conformer should be experimentally feasible. The crystal structures of the complexes in the solid state correspond favourably with the DFT calculated structures. Natural bond orbital second-order perturbation theory calculations indicated donor–acceptor interactions between a furyl oxygen lone pair and the antibonding orbital of the NH for the Mo aminocarbene complexes, in agreement with the preference for the syn conformation for the Mo aminocarbene complexes in the solid state structures.

An experimental and computational study of Fischer Mo carbene complexes gives insight into the conformational preferences of the complexes.Figure optionsDownload as PowerPoint slide