A bulky bis N-heterocyclic carbene complex of iron with coordination number of six: [CpFe(CO)(CH2(ImtBu)2)]I (where ImtBu = 3-tert-butyl-1H-imidazol-1-yl-2(3H)-ylidene)

The crystal structure of the title compound, [CpFe(CO)(CH2(ImtBu)2)]I (where ImtBu = 3-tert-butyl-1H-imidazol-1-yl-2(3H)-ylidene) (1), has been studied by X-ray diffraction. A piano-stool geometry is observed with binding of the Cp ring in three coordination sites, the chelating bis N-heterocyclic carbene (NHC) ligand in two sites, and the CO ligand. This molecule is a cation and the iodide provides a counter-anion that is not coordinated. This structure is similar to other bidentate chelating NHC complexes in the literature, but the combination of t-butyl groups in a pseudo-six-coordinate complex makes the title compound more sterically crowded than its literature analogs. This complex is remarkably stable, with attempts to displace the CO ligand proving unsuccessful and leading to no reaction or decomposition under forcing conditions.