Bite-angle bending as a key for understanding group-10 metal reactivity of d(10)-[M(NHC)(2)] complexes with sterically modest NHC ligands

Synthesis, characterization and investigations on the reactivity of the novel metal basic, yet isolable 14 VE NHC-complexes [M(0)(iPr(2)Im)(2)] (M = Pd 3, Pt 4; iPr(2)Im = 1,3-di-isopropyl-imidazolin-2-ylidene; VE = valence electron; NHC = N-heterocyclic carbene) is reported and compared to the chemistry of the corresponding nickel complex. Quantum chemical analyses reveal that differences in the reactivity of group 10 NHC complexes are caused by differences in the rigidity and thus activation strain associated with bending the corresponding d(10)-[M(NHC)(2)] fragments during reaction. These results should have implications for the understanding of the fundamental steps in catalytic cycles, in which such complex fragments are employed.