COBALT(3)-PROMOTED AMIDOLYSIS OF GLYCINE ETHYL ESTER . AN EXAMPLE OF INTERNAL NUCLEOPHILIC DISPLACEMENT

Treatment of [Co(NH3)5(NH2CH2CO2C2H5)]Br3 with OH- in the pH range 9-14 results in the formation of both [Co(NH3)5(NH2CH2CO2)]2+ (containing the monodentate glycinate anion) and [Co(NH3)4(NH2CH2CO-NH)]2+ (containing glycine imide chelated through both N atoms). Rate data fit the rate law d/dt {[Co(NH3)5(NH2-CH2C2C2H5)]3+} = {k1OH-] +K2[OH-]2 {[Co(NH3)E(NH2CH2CO2C2H5)]3+} with k1 = 50 M-1 sec-1 and k2 = 6.6 × 106 M-2 sec-1 at 25° and µ = 0.1 (KN03). The k1 path is shown to result in the monodentate glycinate product, and the k2 path in the formation of the chelated imide. Acid hydrolysis of [Co(NH3)5(NH2CH2C02C2H5)]Br3results exclusively in the formation of [Co(NH3)5(NH2CH2CO2H)]3+. The complexes [Co(NH3)5(NH2CH2CO2)]-Br2·H2O, [Co(NH3)5(NH2CH2CO2H)]C13.H2O, [Co(NH3)5(NH2CH2CO2C2 H5)]Br3·H2O, [Co(NH3)4(NH2CH2CO-NH)](ClO4)2, and [Co(NH3)4NH2CH2C(OH)NH)](ClO4)3 are also described. Pmr spectra establish that protonation of the chelated imide occurs at O rather than at N, to form the chelated iminol tautomer of glycineamide. © 1969, American Chemical Society. All rights reserved.