The bonding of imidazol-2-ylidenes (H(2)Im) in a series of nickel complexes with seemingly different complex fragment group electronegativities, i.e., [Ni(H(2)Im)(3)], [Ni(H(2)Im)(2)], [Ni(H(2)Im)(CO)], [Ni(H(2)Im)-(CO)(2)], and [Ni(H(2)Im)(CO)(3)], was analyzed. This series provides theoretical evidence that the bonding of imidazol-2-ylidene ligands to metal-complex fragments strongly depends on the nature of the ligand environment of the metal complex. An analysis of a series of isostructural complexes D-2h- and D-2d-M(H(2)Im)(2) with different metals (M = Ni, Pd, Pt) reveals that the bonding also strongly depends on the metal used in the complex.
