
TY  - JOUR
A1  - Gahan, LR 
A1  - O'Conner, MJ 
T1  - Solvent Effects on the Racemization of Optically Active Tris(N-substituted carbamodithioato)cobalt (III) Complexes
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1979
VL  - 32
IS  - 8
SP  - 1653
EP  - 1660
KW  - 
UR  - https://doi.org/10.1071/CH9791653 
N2  - The thermal racemization in solution of some optically active tris(N-substituted carbamodithioato)- cobalt(III) complexes [N-substituents = diphenyl, dimethyl, diisopropyl, and tetramethylene (pyrrolidinyl)] has been measured polarimetrically in a range of solvents including dimethylformamide, acetonitrile, carbon tetrachloride, chlorobenzene, chloroform, toluene and ethanol. The metal-centred (&#916; &#8596; &#923;) inversion reactions show first-order kinetics as expected for an intra- molecular process. Thermodynamic activation parameters for the reaction show that values of &#916;S&#8225; occur over a wide range (from -124 to +60 J K-1 mol-1) as do the values of &#916;H&#8225; (from 67·4 to 129·3 kJ mol-1). Values for &#916;G&#8225; are reasonably constant. Although a similar mechanism for the metal-centred inversion is suggested for all compounds in the various solvents because of an observed isokinetic relationship between &#916;H&#8225; and &#916;S&#8225;, with isokinetic temperatures in the range 312-369 K, it is clear that postulates of reaction mechanisms based on the value of &#916;S&#8225; determined in only one solvent should be treated with caution. The optically active (-)546-tris(N,N-diisopropylcarbamodithioato)cobalt(III) complex photoracemizes in solution without decomposition. The rate of photoracemization is solvent-dependent being in the order bromoform » carbon tetrachloride &#8776; chloroform »benzene. 
ER  -

