Transition metal hydrides physical properties

P. V. Geld, R. A. Ryabov, L. P. Mokhracheva, Hydrogen and the Physical Properties of Metals and Alloys Hydrides of the Transition Metals, Nauka, Moscow, 1985. 

The hydrides show the chemical and physical properties one would anticipate from the position of the metal in the periodic table and from the foregoing. The strongly electropositive metals of the first two groups give saline hydrides which physically resemble the corresponding fluorides. The transition metals form metallic or semimetallic hydrides, presumably because of their ability to use d or d-hybrid orbitals which are delocalized into a conduction band. Apart from their metallic character, however, there are no unexpected differences in proper-... 

The interstitial structures comprise the compounds of certain metallic elements, notably the transition metals and those of the lanthanide and actinide series, with the four non-metallic elements hydrogen, boron, carbon and nitrogen. In chapter 8 we discussed the structures of a number of hydrides, borides, carbides and nitrides of the most electropositive metals, and these we found to be typical salt-like compounds with a definite composition and with physical properties entirely different from those of the constituent elements they are generally transparent to light and poor conductors of electricity. The systems now to be considered are strikingly different. They resemble... 

A combination of computational and experimental approaches gives an understanding of the proton-hydride interaction. This new type of hydrogen bond, the dihydrogen bond, is shown to influence the physical properties and reactivities of a number of main group and transition metal compounds. It seems to be important in cases of protonation of hydrides by acids HA. 

Hanada, N., Ichikawa, T. and Fujii, H. (2005) Catalytic effect of nanoparticle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling, Journal of Physical Chemistry B, 109, 7188-7194. 

The maj or exceptions to this simplified picture are probably CuH and ZnH2, which are reported to be stoichiometric, nonmetallic solids like the main group metal hydrides, but their crystal stmctures and physical properties are not well characterized. Borderline cases are the rare earth hydrides, which show a hydrogen concentration-dependent semiconductor-metal transition. E11H2 and YbH2 behave like alkaline earth dihydrides because of the special electron configuration of Eu + (4/ ) and Yb + (4/ " ). 

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