The Influence of the Alkyl Chain Length and Steric Effect on Stability Constants and Extractability of Co(II) Complexes with 1‐Alkyl‐4(5)‐methylimidazoles

Abstract Extraction of Co(II) complexes has been studied with nine derivatives of 1‐alkyl‐4(5)‐methylimidazoles (with R=C2H3 to C10H21) from aqueous solution [I=0.5(KNO3) at 25°C] with toluene, trichloromethane, and 2‐ethyl‐1‐hexanol. Stability constants of the complexes formed in the aqueous phase (β c ) as well as partition constants (P c ) of the extracted species were determined. It was demonstrated that both the stability constants and partition constants of the complexes increase with an increasing of the 1‐alkyl chain length. The tetrahedral together with octahedral complexes were formed beginning from the second step of complexation. Furthermore, the influence of the bulkiness of the 1‐alkyl group on separation process of Co(II) from Zn(II) for extractions with toluene and 2‐ethyl‐1‐hexanol were determined.