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Inbezug auf einen Sn1CB‐Mechanismus, der mittels Deprotonierung über einen 5‐fach koordinierten Zwischenzustand erfolgt, wird der stereochemische Verlauf der basischen Hydrolyse der Titelverbindungen mit den Aminen NH3, Methyl‐, Benzyl‐ und Cyclohexylamin sowie Pyridin, 4‐Picolin, 4‐Benzylpyridin, Lutidine, Isochinolin, Imidazol, N‐Methylimidazol und Benzimidazol untersucht.

Aquation rates forcis‐CoCl(en)2(A)2+ (A = 3,5‐lutidine, imidazole, N‐methylimidazole, benzimidazole) have been determined by halide release titration in 1.0 M HNO3 at 50–80°C. Kinetic parameters are (in the above order of A) 107k298 (sec−1), 7.4, 5.7, 1.3, 9.7; Ea (kJ/mole), 103, 101, 130, 112; log PZ (sec−1), 11.89, 11.53, 16.04, 13.58; ΔS298‡ (J/°K· mole),−26, −32, +54,+7. Rates of racemization for active cis‐Co(en)2(A)‐(OH2)3+ were measured spectropolarimetrically in 0.1 M HClO4, 0.02 M Hg2+ for A = ammonia, cyclohexylamine, 3,5‐lutidine, N‐methylimidazole. Kinetic parameters are (units as above) 109k298 = 1.8, 38.0, 7.7, 1.7; Ea = 150, 135, 152, 157; log PZ = 17.49, 16.18, 18.56, 18.87; ΔS298‡ = +82, +57, +102,+108. Rates of racemization of the active hydroxo complexes cis‐Co(en)2(A)(OH)2+ (A = NH3, CH3NH2, 3,5‐lutidine, imidazole) were measured similarly at pH = 8 (π = 2.0, NaClO4). The racemization of the hydroxo is ca. (3–4) × 103 faster than for the corresponding aqua complex. Kinetic parameters are 106k298 = 2.55, 7.2, 30.1, 7.0; Ea = 138, 123, 122, 128; log PZ = 18.58, 16.39, 16.85, 17.18; ΔS298‡ = +102,+60, +69,+76. Racemization rates for aquahydroxo mixtures (A = CH3NH2, 3,5‐lutidine, imidazole) were also determined in the pH range of 4–8 (θ = 2.0, NaClO4) at 50.6°C, and pKa data calculated from the pH versus k plot are 5.50, 5.65, and 6.40, respectively, for A.

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Aquation rates for cis-CoCl(en)2(A)2+ (A = 3,5-lutidine, imidazole, N-methylimidazole, benzimidazole) have been determined by halide release titration in 1 .O M HNOz at 50-80°C. Kinetic parameters are (in the above order of A) 1O7k29s (sec-I), 7.4, 5.7, 1.3, 9.7; E, (kJ/mole), 103, 101, 130, 112; log PZ (sec-l), 11.89, 11.53, 16.04, 13.58 8, 38.0, 7.7, 1.7; E, = 150, 135, 152, 157; log PZ = 17.49, 16.18, 18.56, 18.87; ASzgsr = +82, +57, +102, +l08. Rates of racemization of the active hydroxo complexes cis-Co(en)z(A)(OH)2+ (A = NH3, C H~N H Z , 3,5-lutidine, imidazole) were measured similarly at pH = 8 ( p = 2.0, NaC104). The racemization of the hydroxo is ca. (3-4) X 103 faster than for the corresponding aqua complex. Kinetic parameters are 106km = 2. 55, 7.2, 30.1, 7.0; E, = 138, 123, 122, 128; log PZ = 18.58, 16.39, 16.85, 17.18; ASZss* = +102, +60, +69, +76. Racemization rates for aquahydroxo mixtures (A = CH3NH2, 3,5-lutidine, imidazole) were also determined in the pH range of 4-8 ( p = 2.0, NaC104) at 50.6"C, and pK, data calculated from the pH versus k plot are 5.50, 5.65, and 6.40, respectively, for A.