Bond dissociation energy values carbon-metal

The low values of dissociation energy of a bond metal-carbon are characteristic particularly for alkyl transition-metal compounds. Some of them are the key intermediates of Ziegler-Natta low-pressure polymerization of alkenes. Outside the laboratory or chemical plant [43, 44], Nature gives us also important representatives of such compounds namely vitamin B12 or coenzyme B12. 

AHi° values of free radicals can be used to derive mean dissociation energies of metal-carbon bonds in metallic alkyls and related compounds. Thus, if both AH ° (MR , g) and AHf° (R, g) are known, the heat of the disruption process... 

Despite their high dissociation energy of 133 kcal/mol, sp C—H bonds are prone to C—H bond activation. Indeed, the simplest alkyne, acetylene, has a rather small pR, value of25—26, which makes it a weak acid in organ-ometaUic chemistry, and can be deprotonated by a strong base such as a nitrogen- or carbon-based anion. Therefore, the reaction between a metal alkyl complex and a primary alkyne is usually thermodynamically favorable and resembles a classical acid—base metathesis reaction. 

---