Steric Effect of 3,5-Bis(trifluoromethyl)phenol as Hydrogen-Bond Donor on Outer-Sphere Complexation in the Synergistic Extraction of Aluminium(III) and Gallium(III) with 2,4-Pentanedione

Abstract

The synergistic extraction of aluminium(III) and gallium(III) with 2,4-pentanedione (Hacac) in heptane from a weakly acidic solution was investigated in the presence of 3,5-bis(trifluoromethyl)phenol (BTMP). A large enhancement of the extraction of metal(III) was ascribed to the formation of outer-sphere complexes between metal(III) chelates and BTMP in the organic phase. Furthermore, an IR study demonstrated that the outer-sphere complexes were formed by the hydrogen bond between the hydroxy hydrogen atom of BTMP and the oxygen atoms of metal(III) chelates. The formation constants of the outer-sphere complexes with BTMP were determined and compared with those with 3,5-dichlorophenol (DCP) to understand the steric effect of the phenol derivative in this synergistic extraction. The bulky trifluoromethyl-group of BTMP and the short oxygen–oxygen nonbonded distance of Al(acac)3 resulted in a steric repulsion between two BTMP molecules to prevent the formation of Al(acac)3·3BTMP, although Al(acac)3·3DCP, Ga(acac)3·3BTMP, and Ga(acac)3·3DCP could be formed. Such a steric effect on outer-sphere complexation improves the separation efficiency between aluminium(III) and gallium(III) in the present synergistic extraction.

Enhanced Extraction of Tris(pentane-2,4-dionato)cobalt(III) in Supercritical Carbon Dioxide/Water Systems by Association with Fluorinated Phenols

“…This modifier effect of fluorine-containing alcohols and PhOH thus resulted in a very useful method to overcome the low solubility of metal complexes in SC-CO 2 . The distribution enhancement of coordinatively saturated chelates with halogen-containing PhOH as hydrogen donors has been extensively reported in liquid-liquid extraction systems [13][14][15][16][17][18][19][20]. Thus, we anticipate that the association between coordinatively saturated chelates and PhOH via hydrogen bonding can be applied to enhance the distribution of coordinately saturated chelates from the aqueous phase to SC-CO 2 during liquid-liquid extraction.…”

“…A known quantity of PhOH was introduced into the mixing cell after which compressed CO 2 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) MPa) was added by the syringe pump and stirred with a magnetic stirrer for 1 h. An aqueous solution (1.54 cm the optical cell, the valve was closed. The solutions in the optical cell were stirred with a magnetic stirrer for 3 h and subsequently settled for 10 min.…”

Association of Tris(pentane-2,4-dionato)chromium(III) with Modifiers of Hydrogen-bond Donors in Supercritical Carbon Dioxide

“…The values of the acid dissociation constant of HFP and BTMP in the aqueous solution at 298 K are 10 -9.3 and 10 -7.6 , respectively. 22,23 These values are larger than that (10 -12.4 ) of TFE, that is, the hydrogen-bond abilities of HFP and BTMP to form the association complex are larger than that of TFE. The solubility of Cr(acac)3 in modified SC-CO2 at 20.3 MPa became larger compared to 10.1 MPa.…”

An extraction study of gallium, indium, and zinc with mixtures of sec-octylphenoxyacetic acid and primary amine N1923

“…In recent years, many synergistic extraction systems have been developed. The mutual mixtures of organophosphorus acids, neutral organophosphorus extractants, carboxylic acids, amines or ammonium salts, quinolines, dichlorophenols, and b-diketones have been reported by many authors [16][17][18][19]. For instance, Choi and Ohashi [18] have studied the large synergistic effect of 3,5-dichlorophenol (HDCP) in the extraction of gallium with 2-methyl-8-quinolinol derivatives (HA).…”