Kinetics and mechanism of a cobalt(III) complex catalyzed hydration of nitriles

[Co(cyclen)(OH 2 ) 2 ] 3+ (1) efficiently catalyzes hydration of acetonitrile to acetamide in a three-step cycle at pH 7, 40 o C (cyclen=1,4,7,11-tetraazacyclododecane). The mechanism involves (a) equilibrium coordination of acetonitrile to 1 (K 1 =2.5 M -1 ) followed by (b) intramolecular metal hydroxide attack on the coordinated nitrile resulting in formation of the chelated acetamide (k 2 =4.7×10 -3 s -1 ) and (c) dissociation of the chelated amide (k 3 =3.3×10 -4 s -1 )