Proton Transfer to a Hydride Ligand in Solution Experimental Observation of Intermediates

Proton Transfer to a Hydride Ligand in Solution Experimental Observation of Intermediates 

Despite the intense investigations, data on H H bond formation rates are rather limited since the process is usually too fast for studies by standard kinetic techniqnes. Nevertheless, some estimations are possible from low-temperatnre NMR spectra, nsually recorded in Freon solutions. These Freon solvents stop MH HX bond formation even on the H NMR time scale. For example, the ReH resonance of [Cp ReH(CO)(NO)] decoalesces in the presence of acidic alcohols at 96 K, giving two resolved lines at —7.54 and —8.87 ppm, assignable to the free and dihydrogen-bonded hydride, respectively [33]. Under these conditions, the lifetime of the MH- HX complexes, x, can be calculated via 

Both IR and NMR techniques can be used to detect M-H HX bonds, transforming to intimate ion pairs, M(t -H2) X , and then to the product of full 

The example above demoustrates the possibilities of variable-temperature NMR. However, the best experimeutal method for observiug iutimate iou pairs, M(ti -H2) X , is the IR spectroscopy. Here besides direct observatiou of 

ENERGY PROEILE OE PROTON TRANSEER TO A HYDRIDE LIGAND IN SOLUTION 

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