H -Assisted Removal

Studies on the removal of unidentates in acid media have been made mainly with inert complexes. It might be expected that the removal of ligands that retain some basicity, even when coordinated, would be acid-promoted, e.g. 

Sometimes appreciable amounts of CrXH + build up and the full rate law (4.35) is applicable, as with X = CH3C02, Ref. 60. Normally however, K [H ], and 

Placing a proton on the X group presumably weakens the Cr-X bond. The enhanced lability is due to a reduced enthalpy of activation, compared with that associated with the step. Normally, the removal of unidentate ammonia or amine ligands from metal complexes is not accelerated by acid, since the nitrogen is coordinately saturated. This situation changes when we consider multidentates (Sec. 4.4.2). 

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