Polyhydrido complexes

The second general method involves the protonation of a polyhydrido complex using a strong acid such as HBFa.EtiO. Typical examples involving d, d , d or d metal centres are ... 

Treatment of polyhydrido complexes with diazonium salt, even in an excess, never results in the formation of more than a mono(diazene) complex (62, 218, 331) fEq. (24)1. 

Cui, D.M., Tardif, O., and Hou, Z.M. (2004) Tetranuclear rare earth metal polyhydrido complexes composed of (C5Me4SiMe3)LnH2 units. Unique reactivities toward unsaturated C-C, C-N, and C-O bonds. Journal of the American Chemical Society, 126, 1312. 

Li, X., Baldamus, J., Nishiura, M. et al. (2006) Cationic rare-earth polyhydrido complexes synthesis, structure, and catalytic activity for the cis-1,4-select polymerization of 1,3-cyclohexadiene. Angewandte Chemie International Edition, 45, 8184. 

Another parameter that may be very relevant to the structural characterization of polyhydrido complexes in both solution and sohd is the deuterium quadrupole coupling constant (CQ).47,74 78 Formation of a chemical bond creates a strong nonhomogeneous electric field along its direction (z axis) measurable by the electric... 

These reactions are well known in simple polyhydrido-complexes, and are merely a consequence of rapid proton/hydride exchange at the metal site [51] as shown in Figure 8. 

It has been well known for many years that coordinatively-saturated polyhydrido-complexes can bind molecules and ions by displacement of dihydrogen. The mechanism of this reaction is shown in its simplest form in Equation (12), in which the coupling of two hydride ligands and reductive-elimination of dihydrogen generates a transient coordinatively-unsaturated intermediate which is subsequently attacked by molecules or ions. 

The ability of protonation to facilitate release of dihydrogen from simple polyhydrido-complexes was not unknown before the mechanism of nitrogenase was proposed, but it was only in work inspired by these proposals that it was appreciated how versatile this mode of activation can be. A particularly versatile system which shows a variety of different reactivities (depending on the substrate) is now presented. 

Polyhydrido complexes are often utilized for the CH bond activation, for example, ReH7(PCy3)2/ During heating of this complex in (333-353 K) reductive... 

Hou, Z.M., Nishiura, M., and Shima, T. (2007) Synthesis and reactions of polynuclear polyhydrido rare earth metal complexes containing (C5Me4SiMe3)LnH2 units a new frontier in rare earth metal hydride chemistry. European Journal of Inorganic Chemistry, 2535. 

Cationic lanthanide hydrido clusters have also been s)mthesized by treating the neutral polyhydrido clusters with Ph3CB(CgF5)4 (Li et al., 2006b). The structures of two such complexes are illustrated in Figure 57. 

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