Highly effective extraction of iron(III) with 4-isopropyltropolone in nonpolar solvents containing 3,5-dichlorophenol as a synergist

A great enhancement in the extraction of iron(III) with 4-isopropyltropolon e (Hipt) has been observed upon the addition of 3,5-dichlorophenol (DCP) as a hydrogen-bond donor, and highly efficient synergistic extraction system for iron(III) was presented using nonpolar solvents such as heptane and cyc lohexane. An equilibrium study of the heptane system has demonstrated the f ormation of the adduct complexes of not only the iron(III) chelate, Fe(ipt) (3).nDCP (n = 1 - 3), but the reagent, Hipt.nDCP (n = 1, 2). The formation constants (beta (M,n) = [Fe(ipt)(3).nDCP](org)/[Fe(ipt)(3)](org)[DCP](org)( n), beta (H,n) = [Hipt.nDCP](org)/[Hipt](org)[DCP](org)(n))of the correspon ding complexes were determined and evaluated by comparing with those of ace tylacetone (Hacac). The values obtained for Fe(ipt)(3) and Hipt were larger than those for Fe(acac)s and Hacac, respectively, suggesting the higher hy drogen-bond accepting power and basicity of the former ligand.