Octahedral chromium(III) complexes in dipolar aprotic solvents. II. The isomerization of cis- and trans-[CrCl2 en2]+ ions in anhydrous dimethyl sulphoxide

Abstract

The equilibria represented by the following equations: (See diagram in paper) have been studied in anhydrous dimethyl sulphoxide at various chloride ion concentrations. The mechanisms of the reactions are interpreted as dissociative and this assignment is consistent with the radiochloride exchange data. The kinetic and equilibria results are dependent on ion association which is separately treated by conductance measurements in the case of cis-[CrCl2 en2]+Cl-. Activation energies are recorded.

Reactions of cis- and trans-bromo(dimethylformamide) and bis(dimethylformamide)bis(ethylenediamine)chromium(III) in dimethylformamide. Kinetics, stereochemistry, and equilibriums

“…The pseudo-first-order rate constant for the conversion of complex 1 to complex 2 is labeled ki2, and similarly for the other paths shown. 3 The primary solvolyses 1 -* 2 and 4 -* 5 have been considered previously1 and we now turn to the other reactions.…”

“…However, it is apparent that each of the two products is directly formed since, particularly at an early stage of reaction (less than 1/2), product interconversion is too slow to account for the constant product ratio on the basis of exclusive czT-Cr(en)2(DMF)Br2+ or m-Cr(en)2(DMF)2.3+ formation followed by "instantaneous" equilibration. Product interconversion might have been expected to be evident as a shift in isosbestic points after about lii/2 of Zz*izro-Cr(en)2(DMF)Br2+ reaction since this is [3][4][5] times as fast as the initial reaction. However, the isosbestic points remain sharp since the equilibrium distribution perchance closely corresponds to the kinetic proportions at all temperatures investigated.…”

Kinetics and stereochemistry of solvolysis of cis- and trans-dibromo- and bromochlorobis(ethylenediamine)chromium(III) complexes in dipolar aprotic solvents

“…cis-[Cr(en)2Ck] Cl-HzO, 14 5 recrystallized from water-hydrochloric acid (10 Af)-ethanol (1:1:1), was converted to the bromide ( 2 ) and then to cis-[Cr(en)2Bn] Br-FbO by a known method16 modified as described now.…”