BASE HYDROLYSIS OF THE (+)589-CIS-[CO(EN)2X(GLYO)]+ IONS (X-=CL-,BR-) AND THE IMPORTANCE OF ION-PAIRS

Base hydrolysis of A-(+)589-cw-[Co(en)2X(glyO)]+ ions (X= CI, Br; glyO = glycinate anion) gives 40.8% [Co(en)2(glyO)]2+(32.1% A, 8.7% A), 49.3% ci-[Co(en)2OH(glyO)]+ (35.8% A, 13.5% A), and 9.9% rrani-[Co(en)2OH(glyO)]+ in 1.0 mol dm3 NaOH and 46.1% [Co(en)2(glyO)]2+ (36.2% A, 9.9% A), 45.1% ris-[Co(en)2OH(glyO)]+ (32.8% A, 12.3% A), and 8.8% i/ww-[Co(en)2OH(glyO)]+ in the pH range 10.0-13.0. Addition of NaN3 results in A-cis, A-cis-, and trans-[Co(en)2N3(glyO)]+ products in addition to [Co(en)2(glyO)]2+ and A-cis, A-cis-, and ranj-[Co(en)2OH(glyO)]+, but the [Co(en)2(glyO)]2+ yield is affected more than the latter. The rates of base hydrolysis of the ions cw-[Co(en)2Br(amine)]2++at 25.0C and nm (amine, 0h (mol-1 dm3 s1): glycylglycine isopropylester, 730; glycylglycinate anion, 470; glycinamide, 628; glycinate anion, 82) are reduced in NaC104,KC1, and Na2S04 solutions, but the effect on cw-[Co(en)2Br(glyO)]+is less than the others. The results are interpreted in terms of internal ion pairing by the glycinate carboxylate anion with competition by N3, C104, CI, and S04 2 for the internal ion pair. The mechanism of base hydrolysis and the question of intermediates are discussed. © 1979, American Chemical Society. All rights reserved.