Transition metal hydrides stability

Transition metal hydrides play a key role in the catalytic homogeneous isomerization of olefins. The pure hydrides such as HCo(CO)4 can function as the catalyst, or transition metals complexed to stabilizing ligands can function as catalysts the catalysis almost certainly proceeds through hydride intermediates in many cases. 

Mdssbauer spectra of bonding and structure in, 15 184-187 reactions with diborane, 16 213 stabilization of, 5 17, 18-19 cyanates, 17 297, 298 cyanide complexes of, 8 143-144 cyclometallated bipyridine complex, 30 76 diazene complexes, 27 231-232 dinitrogen complexes, 27 215, 217 diphosphine complexes of, 14 208-219 dithiocarbamates, 23 253-254 -1,2-dithiolene complexes, 22 323-327 hydrogen bonding, 22 327 halide complexes with phosphine, etc., 6 25 hexaflouride, structure, 27 104 hydride complexes, 20 235, 248-281, see also Transition metal-hydride complexes... 

Hydroperoxides result from oxidation of transition metal hydride complexes, but since so many transition metal hydrides possess oxidatively sensitive ligands, such as phosphines or CO, it is less likely that hydroperoxides may be intercepted. An interesting example of a stable hydroperoxide is the [(NH3)sRh(OOH)] cation . The hydride from which this species derives is one of the few that is not stabilized by soft, oxidizable ligands. 

Transition-metal hydride complexes which also contain tertiary phosphines as stabilizing ligands are among the most numerous and stable of presently known hydride complexes. Their relative ease of preparation, and their thermal and oxidative stability, make them suitable materials for carrying out detailed studies of the metal-hydrogen system. As shown in Table III, a considerable range of complexes in this class has been prepared and their infrared and proton magnetic resonance spectra have been studied. The results of these studies are discussed in Section II,B and C, respectively. 

Blomqvist, H. (2003) Magnesium ions stabilizing solid-state transition metal hydrides. Ph.D. thesis, Stockholm University. 

The first hydride complex investigated by the neutron diffraction technique was K2[ReH9] containing the terminal M—H linkage. Many examples of complexes containing the terminal hydride ligands are now known for virtually all d-block transition elements. Binary transition-metal hydrides are rather few and the majority are stabilized by carbonyl, phosphine, or other ancillary ligands. 

Many complexes are known which contain one or more hydrogens directiy attached to a transition metal by an essentially covalent bond [2,3]. The occurrence and stability of these complexes frequently parallels that of metal-alkyl complexes. Thus thermally stable transition metal-hydrides are found when the complexes are kinetically staUe, that is, they often... 

The propagation centers also react with the inhibitors inevitably present in the reaction medium. The interaction with coordination inhibitors may stabilize the transition metal-carbon bond, as the elimination of the coordinative insufficiency of the transition metal ion makes it impossible for the metal-carbon bond to rupture through the mechanism of the /3-hydride shift. 

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