Dihydrogen Complexation

Abstract

Dihydrogen complexation with retention of the H-H bond, once an exotic concept, has by now appeared in a very wide range of contexts. Three structural types are currently recognized: Kubas dihydrogen, stretched dihydrogen, and compressed dihydrides. These can be difficult to distinguish, hence the development of a number of novel spectroscopic methods for doing so, mainly based on NMR spectroscopy. Three important reactivity patterns are identified: proton loss, oxidative addition, and dissociation, each of which often contributes to larger reaction schemes, as in homogeneous hydroformylation. Main group examples are beginning to appear, although here it is mainly by computational studies that the relevant structures can be identified. Enzymes such as the hydrogenases and nitrogenases are also proposed to involve these structures.

Photoinduced Reductive Elimination of H2 from the Nitrogenase Dihydride (Janus) State Involves a FeMo-cofactor-H2 Intermediate

“…Although we as yet have no direct evidence as to the structure of the observed B intermediate (Fig 4), as visualized in Fig 6 the behavior of inorganic H 2 complexes 30–32 indicates that this intermediate is an H 2 -bound state on the ground adiabatic potential-energy surface, a possibility first noted thirty years ago. 33 Firstly, thermally induced re/oa of inorganic H 2 complexes generally proceed through such an intermediate, 23 indicating an expectation that such a state is present on the ground adiabatic surface as shown in Fig 6.…”

Competing Pathways in the Photochemistry of Ru(H)2(CO)(PPh3)3

“…36 Furthermore, the disappearance of 2 upon warming is consistent with the well-known lability of dihydrogen as a two-electron-donor ligand. 37 Complex 2 is an analogue of Ru(H) 2 41,42 In order to confirm the presence of a dihydrogen ligand in 2, data for T 1 were recorded at 400 MHz between 212 and 242 K for the resonance at δ −5.82. The value of T 1 (min) for 2 proved to be 35 ± 2 ms at ca.…”

Engineering the Frontier Orbitals of a Diazadiborinine for Facile Activation of H2, NH3, and an Isonitrile

“…Exposure of ab enzene solution of 4 to H 2 (1 bar) at 70 8 8Cf or 5h resulted in ac olorless solution, from which compound 5 was isolated as aw hite powder in 72 %y ield. [2,12] Tr eatment of 4 with one equivalent of DCNxyl (xyl = 2,6-dimethylphenyl) in toluene at room temperature led instantaneously and cleanly to the formation of compound 7.The 11 BNMR spectrum of 7 displayed broad singlets at 3.6 ppm and À12.9 ppm. Thesolid-state IR spectrum of 5 exhibited two characteristic B À Hv ibrations at 2442 and 2326 cm À1 .X -ray diffraction revealed that two boron-bound hydrogen atoms are attached on the same side of the B 2 C 2 N 2 six-membered ring, the selectivity of which is similar to that for I.…”