Abstract: | The kinetics and mechanism of the hydrolysis of several cyano(pyrrolyl-1)borates in aqueous medium has been investigated. The hydrolysis of cyanophenyl(pyrrolyl-1)-borates, cyano(tripyrrolyl-1)borate and cyanohydro(pyrrolyl-1)borates proceeds via two kinds of reactions; (a) a special H+ ion catalyzed reaction (A-1 mechanism) and (b) a H+ ion concentration-independent process of SN1 mechanism. In acidic medium the BH2(NC4H4)CN]− anion is reversibly protonated at the -carbon of the pyrrolyl group and a product with composition C4H5N · BH2CN, stable towards hydrolysis is also formed. In the H+ ion catalyzed reaction the B---N bond very likely breaks, whereas upon the H+] ion concentration-independent reaction a B---CN cleavage occurs. The presence of the cyano substituent significantly increases the hydrolytic stability of the B---N bond, whereas the pyrrolyl-1-substitution remarkably decreases the stability of the B---CN bonding. |