Metal-hydrogen bond strength

Because of the lower metal-carbon and metal-hydrogen bond strength, organolead hydrides are particularly unstable species and represent the least stable of those of the group 14 elements. Triorganolead hydrides are obtained at low temperatures by reduction of the halides with LiAlH4 (equation 45), but they decompose at 0 °C. 

The relative decomposition temperatures for the formate, 7, on the clean metals (M) can be related to the surface metal-oxygen and metal-hydrogen bond strengths listed in Table V. With the exception of silver, TJ, decreased... 

This is one of the first specific examples of a ternary transition state for oxidative addition, one of the characteristic reactions of metal radicals as shown generally in Scheme 10.1. In addition, the transition metal-hydrogen bond strength (58 kcal/mol) was determined for H-Co(CN)s2-—one of the first accurate determinations. A... 

Table 3.1. Comparison of metal hydrogen bond strengths (kcal/mol).

Hydrogen dissociates on all metals already at low temperatures only on copper is the dissociation activated. The metal-hydrogen bond strength varies little with the substrate metal, differences in surface structure are more important. As the recom-binative desorption of hydrogen atoms is a rapid process, the surface coverage of hydrogen is usually low at typical reaction temperatures. 

There is almost no reliable information about the strength of metal-hydrogen bonds in organometallic compounds. Earlier (Section 2.2.) it was established that M-H bonds formed by (spontaneous) -elimination from metal alkyls should be stronger that their precursor, but this is an unsatisfactory and imprecise position. The dissociation... 

J. A. Martinho Simoes, J. L. Beauchamp. Transition Metal-Hydrogen and Metal-Carbon Bond Strengths The Keys to Catalysis. Chem. Rev. 1990, 90, 629-688. 

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