Hydrido transition metal

The hydrido-transition metal cluster complexes. A. P. Humphries and H. D. Kaesz, Prog. Inorg. Chem, 1979, 25,145-222 (244). 

Kaesz, H. D., Hydrido Transition-Metal Cluster Complexes, Chem. Br. (1973) 9,... 

Hydrogen-Deuterium Exchange in Hydrido Transition Metal Cluster Complexes... 

Fig. 14. A schematic cycle for COz-reduction by an hydrido transition metal homogeneous catalyst...

TABLE 1 Hydrido-Transition Metal Complexes Appearing in Inorganic Synthesis Vol. 2-16 ... 

An interesting feature of hydrido transition metal-PF3 complexes is that apart from a few dinuclear systems (Section VI) only mononuclear systems are so far known and there is as yet no corresponding chemistry analogous to that of polynuclear carbonyl hydrido compounds. The trifluorophosphine metal hydrido compounds are usually highly acidic and can readily form metallate ions such as [M(PF3)m]x and [MH(PF3) r. 

In favorable cases, homogeneous catalytic hydrogenation of organic substrates such as olefins also may be achieved by transfer of hydrogen from the hydrido-transition metal complex. The following examples, all discovered within the last few years, illustrate how this can be realized for each of the three mechanisms of splitting of hydrogen (heterolytic, homolytic, and insertion) described above. 

There seems to be some confusion about the polarization of the metal-hydrogen bond in certain hydrido-transition metal-carbonyl compounds, in particular HCo(CO)4. This and some related hydrido-carbonyl compounds are slightly soluble in water, and such solutions are clearly acidic In the gas phase or in non-polar solvents, however, these complexes exhibit spectroscopic and chemical properties similar to those of other non-acidic hydride complexes. A MO calculation of the charge densities in HCo(CO)4 indicated that 1.6 electrons are associated with the hydrogen atom, and the question was discussed as to how a molecule with a negative-... 

Kristjansdottir, S.S., and Norton, ).R. (1991) Acidity of hydrido transition metal complexes in solution, in Transition Metal Hydrides (ed. A. Dedieu), VCH, New York, (Chapter 9), pp. 309-359. 

Kristjansddttir, S. S. Norton, J. R. Acidity of Hydrido Transition Metal Complexes in Solution. In Transition Metal Hydrides Recent Advances in Theory and Experiment, A. Dedieu, Editor VCH New York, 1990. Tables with pAa values of some transition metal hydride complexes. 

Halpern has utilized the principles of reactivity or coordination compounds to explain reaction mechanisms, some examples of which involve metal 7r-complexes. His concept of hydrogenation of olefins is based upon the formation and cleavage of a hydrido transition metal complex. 

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