BASE HYDROLYSIS AND MERCURY(II)-CATALYZED AQUATION OF THE CHLOROPENTAMINE 2)(BETA-ALAOH)CL](2-[CO(EN)(2)(BETA-ALAOME)CL](2+) IN BASIC SOLUTION() AND THE REACTIONS OF CIS)

The complexes cis-[Co(en)(2)(NH2CH2CH2CO2H)Cl](2+) and cis-[Co(en)(2)( NH2 CH(2)CH(2)CO(2)Me)Cl](2+) (en = 1,2-diaminoethane have been prepar ed. The pK of the carboxyl group of the N-coordinated amino acid is 3. 76, very comparable with the value of 3.55 for the pK of NH3+CH2CH2CO2 H. Base hydrolysis of the chloride ligand in cis-[CoCl(en)(2)(NH2CH2CH 2CO2)](+) has been studied by pH-stat over the pH range 9.0-9.6 giving k(OH) = 11.9 dm(3) mol(-1) s(-1) at I = 0.10 mol dm(-3) and 25 degree s C. Spectrophotometric monitoring of the hydrolysis gave k(OH) = 11.2 dm(3) mol(-1) s(-1) under the same conditions. The initial product of base hydrolysis is the hydroxopentamine. The Hg(II)-promoted hydrolys is of the chloropentamine follows the rate expression k(obs) = k(aq) k(Hg)[Hg(II)] with k(aq) = 3.5 x 10(-4) s(-1) and k(Hg) = 2.1 x 10(-2 ) dm(3) mol(-1) s(-1) at 32 degrees C and I = 1.00 mol dm(-3) Base hyd rolysis of the N-coordinated ester complex was studied by pH-stat. The reaction is biphasic with k(OH) = 25.3 dm(3) mol(-1) s(-1) for the in itial reaction. Values of k(OH) for the second reaction decrease as th e pH is raised, falling in the range 9.5-6.5 dm(3) mol(-1) s(-1) at 25 degrees C. Stopped-flow measurements at 490 nm indicated a single rea ction with k(OH) = 12.6 dm(3) mol(-1) s(-1) assigned to chloride hydro lysis. The pH-stat behaviour can be rationalized in terms of formation of the two complexes [Co(en)(2)(OH)(NH2CH2CH2CO2-)](+) and [Co(en)(2) (NH2CH2CH2CO2)](2+) and their mechanism of formation is discussed in d etail.