Octahedral cobalt(III) complexes in dipolar aprotic solvents. V. The substitution of chloride and thiocyanate into the cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion in anhydrous NN-dimethylformamide

Abstract

The kinetics and mechanism of the substitution of chloride ion and thiocyanate ion into the cis-chlorodimethylformamidebisethylenediaminecobalt(111) ion, cis-[CoCl(DMF) en2]2+, have been studied in ,NN-dimethylformamide (DMF). The chloride entry shows mixed kinetics which are accounted for by two paths, a slow ion pair dissociation, and a fast bimolecular attack of chloride on an ion pair. The steric course of the reaction, which is chloride dependent, shows that the ion pair dissociative mechanism is more important at low chloride concentrations. The thiocyanate entry shows similar characteristics. Thiocyanate enters faster than chloride in the bimolecular path, but in the ion pair dissociative path, which is significant at lower anion concentration, both chloride and thiocyanate enter at the same rate.

Kinetics and mechanism of substitution reactions of (dimethylsulfoxide)pentaamminecobalt(III) ion in dimethylsulfoxide solvent: complications due to redox and conjugate base processes

“…In any event, it appears that our present findings do not detract from the usefulness of the extensive contributions of Watts' school (13,(33)(34)(35)(36)(37) and others (e.g., 11) in this field, but future work should include routine checks for con.jugate base and redox pathways.…”

“…Anal) tical reagent grade p-tolue~iesulfonic acid hydrate (Fisher Scientific Company) was used without further recry~tallization. Dirnetli) lsulfoxide (ACS grade, Fisher Chemical Corp.) and DbISO-c16 (Merck, Sharp and Dohme Canada Ltd.) \\ere puritied by a methoci analogo~ti to the purification of D M F as described elsewliere (13).…”

Substitution at chromium(III) centers in aprotic solvents. Ion pairing, anation, and solvent exchange in N,N-dimethylformamide

“…N,N-Oimethylformamide (reagent grade, Baker Chemical Co.), stored over 4A molecular sieve (Guild Corp.), was fractionally distilled under vacuum as previously described. 15 Anhydrous L1CIO4 (City Chemical Co.) was recrystallized from hot water as LÍCIO4GH2O by a slow evaporation of the solution. Water of recrystallization was removed by heating the hydrated salt at 110 °C for 5 days.…”