Dihydrogen complexes stability

J. Eckert, A. Albinati, U.E. Bucher L.M. Venanzi (1996). Inorg. Chem., 35, 1292-1294. Nature of the Rh-H2 bond in a dihydrogen complex stabilized only by nitrogen donors. Inelastic neutron scattering study of [TpMe2RhH2 (TI2-H2)] (TpMe2 = Hydrotris(3,5-dimethyIpyrazolyl)borate). 

Dihydrogen complexes, osmium, 37 3(X)-301 Dihydroxo-bridged complexes acid-base equilibria, 32 108-110 quantitative considerations, 32 115-118 binuclear, 32 66-67 crystallographic data, 32 61, 63 stability complexes, 32 103-104... 

The precursor for the dihydrogen complex here contains a so-called agostic interaction [26], that is an intramolecular interaction of a C-H bond with the metal that stabilizes the electronically (16-electron) and coordinatively unsaturated W(CO)3(PTr3)2 species. It is noteworthy that the splitting/formation of the H-H bond is much slower here than its binding to and dissociation from the metal. 

The measurement of HD coupling has been used to derive reliable values for dun in a large number of hydrogen complexes. This is particularly useful for cases where the complexes lack sufficient stability to be isolated at room temperature. For example, (CO)5Cr(H2) was characterized as a dihydrogen complex by this method, although this complex cannot be isolated at room temperature. In the monodeuterated species (CO)sCr(HD), the observed /hd = 35.8 Hz, which leads to dHH = 0.84 A (Figure 5.5). This observation is helpful in interpreting the relaxation time (7)) data as noted above, where two different values for derived from the relaxation data. The HD... 

Finally, insertion of alkynes into dihydrogen mononuclear cationic rhenium complexes, stabilized by the triphos (= l,l,l-tris(diphenylphosphinomethyl)ethane) ligand, leads to vinylidene derivatives which react with water or ethanol eliminating silanols or methane, Fig. 18. Solvents were acetone or THF no chromatography was used. 

Table 11.1. N2 and CO Force Constant and Stretching Frequency Data as a Predictive Tool for the Stability of Dihydrogen Complexes (Reference 13)...

The relative stabilities of these dihydrogen complexes in liquid Xe are W > Cr Mo. Gr(GO)5(H2) and W(G0)5(H2) have recently been characterized by NMR in solution at 190-220 After the initial liquefied Xe work on Gr(GO)s(H2), subsequent matrix experiments characterized dihydrogen complexes using IR bands... 

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