Carbon-hydrogen and hydrogen-hydrogen activation in transition metal complexes and on surfaces

Structural and dynamic properties of propane coordinated to TpRh(CNR) from a confrontation between theory and experiment

“…It is thus clear that decoordination of the pyrazole is needed for proper coordination of the alkane. The reorientation of the C-H bond with respect to the metal-H direction is a well established phenomenon that has been shown by the calculations of Saillard and Hoffmann (31). Similar results are found for the approach to the methylene group of propane, although one sees that the isopropyl group rotates from being perpendicular to the developing square plane to being parallel to the plane as the Rh-C bond forms.…”

“…The propane approaches [Rh] in the plane containing the axial pyrazole and the isocyanide, with the C-H bond pointing toward Rh (the Rh-H-C angle is 180°). This approach is well documented for the approach of an alkane to a planar d 8 complex (31). At this stage, the three pyrazole ligands are bonded to Rh.…”

Potential-energy surface forH2dissociation over Pd(100)

“…at a point were the H-H interaction is significantly weakened and and strong H-metal bonds are already beeing formed 18,34 . Those results, which are not consistent with the Harris-Andersson model 32 , have been consistently explained within a reactivity model 18,34,38 related to the frontier orbital concept 33,39 . Superimposed to the interaction of the hydrogen molecule with the s, pstates of the metal, which gives rise to energy barriers found at simple metals, there is a contribution due to the direct interaction of H 2 with the metal d-states.…”

Nickel hydrogenases: in search of the active site

“…Since 1984 it has become clear that, as discovered by Kubas et al [118], in a number of model compounds of transition metals molecular hydrogen can act as a ligand [50,98,119] in a side-on configuration [164]. This led Crabtree [50] to propose that dihydrogen might well be a ligand to Ni(III) in hydrogenases.…”