Inversion and Deuteration at the Chiral Nitrogen Centers of [Co(acac or ox)2(Me-en or Me3en)]+or− (acac=2,4-Pentanedionate Ion; ox=Oxalate Ion; Me-en=N-Methylethylenediamine, Me3en=N,N,N′-Trimethylethylenediamine)

Abstract

Abstract The rates of the base-catalyzed proton exchange (deuteration, kD) and isomerization (epimerization, kep) at the chiral amine nitrogen centers of [Co(acac or ox)2(Me-en or Me3en)]+or− in aqueous solutions were measured at 34.0 °C, and the results were compared with one another and with those of related complexes. The deuteration rate is affected more by the nature of coexisting ligands than the overall charge on the complex. The uninegative ox complexes have larger kD values than the unipositive acac complexes. The kep values of the ox complexes are ca. 104 times as large as those of the acac complexes. For both ox and acac complexes, the complexes with Me3en have larger kD and kep values than the complexes with Me-en. The deuteration rates are ca. 104–105 and ca. 102 times greater than the inversion rates for the acac and ox complexes, respectively.