Protonolysis is the cleavage of achemical bond by acids. Many examples are found inorganometallic chemistry since the reaction requires polar Mδ+-Rδ- bonds, where δ+ and δ- signify partial positive and negative charges associated with the bonding atoms. When compounds containing these bonds are treated with acid (HX), these bonds cleave:
Hydrolysis (X− = OH−) is a special case of protonolysis. Compounds susceptible to hydrolysis often undergo protonolysis.
Theborohydrideanion is susceptible to reaction with even weak acids, resulting protonolysis of one or more B-H bonds. Protonolysis ofsodium borohydride withacetic acid givestriacetoxyborohydride:[1]
Related reactions occur for hydrides of other electropositive elements, e.g.lithium aluminium hydride.
The alkyl derivatives of many metals undergo protonolysis. For the alkyls of very electropositive metals (zinc, magnesium, and lithium), water is sufficiently acidic, in which case the reaction is called hydrolysis. Protonolysis withmineral acids is sometimes used to remove organic ligands from a metal center.[2]
Inorganic materials with highly charged anions are often susceptible to protonolysis. Derivatives of nitride (N3−), phosphides (P3−), and silicides (Si4−) hydrolyze to giveammonia,phosphine, andsilane. Analogous reactions occur with molecular compounds with M-NR2, M-PR2, and M-SiR3 bonds.[3]