Studies on Polydentate Organic Phosphorus Compounds as Extraction Reagents.

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The following polydentate phosphine oxides have been synthesized in the present work and their possible use as extraction reagents has been examined being compared with the monodentate ligand, Trioctylphosphine oxide (TOPO). Tetraphenyldiphosphine dioxide (TPDPDO), bis (diphenylphosphinyl) methane (BDPPM) and ethane (BDPPE) as bidentate ligands, and tris (diphenylphosphinyl) methane (TDPPM) as a tridentate ligand.The ion pair extraction of divalent metals with these phosphine oxides and a bulky anion has been investigated. It was found that alkaline earths (Mg, Ca, Sr and Ba) and some divalent transition metals (Co, Ni, Cu, Zn and Cd) are readily extracted with BDPPM or TDPPM and perchlorate or picrate ion. The extraction with TOPO or BDPPE was very poor. Six-membered ring which is known to be very stable is formed when BDPPM or TDPPM attaches to a metal ion, whereas seven-membered ring is expected with BDPPE. Precipitate was observed at the benzene/water interface in the BDPPM/ClO_4 system. Picrate is a suitable anion rather than perchlorate. The compositions of the extracted species were obtained by a graphical method.The synergic extraction of divalent metals with 1-Phenyl-3-Methyl-4-Benzoyl-5-Pyrazolone (HPMBP) or 4-trifluoroacetyl-5-pyrazolone (HPMTFP) and phosphine oxides has also been examined. BDPPM was found to be a much more powerful adduct forming ligand than TOPO and BDPPE. TDPPM is considered to work as a bidentate ligand in the synergic extraction of alkaline earths. The stability of the adduct forming reaction and the number of neutral ligand participating in the reaction could be interpreted in terms of the vacant coordination number, the size of room allowed for the neutral ligand and the molecular structure of the neutral ligand.