Crystal structures hydrogen-metal compounds

We have seen how elegantly transition metals can template the formation of knots, but what about Nature s favourite templating interaction, the hydrogen bond A remarkably efficient molecular trefoil knot synthesis based on this interaction was reported by Vogtle and co-workers, who made a knotane in 20% yield [39]. This amazing route (Fig. 11) was uncovered serendipitously during the synthesis of catenanes. The crystal structure of the compound was the definitive proof for the structure, because neither NMR nor mass spectrometry could tell it apart conclusively from the macrocycles that are also formed. 

Homogeneous hydrogenation is often claimed to proceed via an intermediate in which both the olefin and the hydrogen are co-ordinated to the metal of the catalyst complex, though such hypotheses are rarely supported by the isolation and characterisation of such an intermediate. However, for reduction of activated olefins, for example cyano-olefins, in the presence of Ir(H)(CO)(PPh3)s, intermediates of the formula ir(H)(CO)(PPh3)2(olefin) have been isolated, and the crystal structure of the compound with /m 5 -l,2-dicyanoethylene as the olefin has been determined. The mechanistic interest of this crystal structure is that it shows the hydridic-hydrogen conveniently situated cis to the co-ordinated olefin ready for transfer. ... 

Hydrides of variable composition are not only formed with pure metals as solvents. A large number of the binary metal hydrides are non-stoichiometric compounds. Non-stoichiometric compounds are in general common for d,f and some p block metals in combination with soft anions such as sulfur, selenium and hydrogen, and also for somewhat harder anions like oxygen. Hard anions such as the halides, sulfates and nitrides form few non-stoichiometric compounds. Two factors are important the crystal structures must allow changes in composition, and the transition metal must have accessible oxidation states. These factors are partly related. FeO,... 

L. Guenee, K. Yvon, Synthesis, crystal structure and hydrogenation properties of the novel metal compound LaNi Mn, J. Alloys Compd. 348 (2003) 176-183. 

One of palladiums unique characteristics is its abihty to absorb 900 times its own volume of hydrogen gas. When the surface of the pure metal is exposed to hydrogen gas (H ), the gas molecules break into atomic hydrogen. These hydrogen atoms then seep into the holes in the crystal structure of the metal. The result is a metallic hydride (PdH that changes palladium from an electrical conductor to a semiconductor. The compound palladium dichloride (PdCl ) also has the ability to absorb large quantities of carbon monoxide (CO). These characteristics are useful for many commercial applications. Palladium is the most reactive of all the platinum family of elements (Ru, Rh, Pd, Os, Is, and Pt.)... 

Determinations of the crystal structures of [Cd(Gly)2X2] (X = Cl or Br) have shown the two compounds to be isomorphous and to involve an octahedral environment about the metal the amino group is hydrogen bonded to a carbonyl group and a halide ion.250... 

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