Metal-hydrogen bond cleavage

R = aryl,dppe = Ph2PCH2CH2PPh2), obtained by protonation of the parent neutral nitrile compounds, undergo, in an aprotic medium and at aPt electrode, metal-hydrogen bond cleavage upon electrochemical oxidation or reduction, and the mechanisms of these distinct electroactivation processes have been investigated (for J[, R C5H4Cl-4) by preparative scale electrolysis, cyclic voltammetry and simulation techniques. 

Nevertheless, our studies indicate that electroinduced metal--hydrogen bond cleavage, either upon oxidation or reduction, can occur through bimolecular processes, following pathways which are considerably more complex than a simple intramolecular rupture of such a bond. 

From Metal-Hydrogen Bond Cleavage Reactions (J-4)... 

This established C-H chemistry in molecular coordination compounds should have its formal analog in metal surface chemistry. Carbon-hydrogen bond-cleavage is a common reaction at metal surfaces but it does not comprise mechanistically the simple collision of a hydrocarbon such as methane with a metal surface vide infra). Methane neither reacts with nor is chemisorbed on a metal surface under moderate conditions. However, propylene does chemisorb, and then C-H bonds may be broken, depending upon the nature of the metal surface. Generally, the sequence at the surface comprises first the formation of a coordinate bond between a surface metal atom(s) and some functionality in the... 

Further chemical evidence for the polarization of the metal-hydrogen bonds as M —H comes from cleavage reactions with aqueous acids, alcohols or phenols to produce H2, or with halogen (Br2 or I2) to give hydrogen halide, although these reactions are sometimes not quantitative. Some examples are ... 

Carbon-Hydrogen Bond Cleavage by Electrophilic Metals... 

Ti -vinyl [Ti2-C(CH2Ph)CH2] or hydride complexes is often followed by chemical steps, and examples of redox induced proton or hydrogen elimination (involving heterolytic or homolytic N-H, C-H or metal-H bond cleavage), nucleophilic attack or isomerization reactions have been presented. 

The metal-hydrogen and metal-carbon bond cleavage reactions have also been exploited in some instances (Section 2.10.2). 

Transition Metal-Carbon Bond Cleavage Through /3-Hydrogen Elimination. 

Kakiuchi, R Kochi, T. Transition-metal-catalyzed carbon-carbon bond formation via carbon-hydrogen bond cleavage. Synthesis (Stuttg) 2008, 3013-3039. 

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