H.K. Saha

Abstract: Reactions of the complex ion [Mo2O4(C2O4)2(H2O)2]2− (I) have been investigated. On acidification with perchloric acid and hydrochloric acid, complex (I) gave molybdenum(V) aqua-dimer ion [Mo2O4(H2O)6]2+, which was converted into the monomeric species [MoOCl5]2− in concentrated hydrochloric acid. The initial reaction of complex (I) with mercaptoacetic acid, giving a complex of stoichiometry 1 ligand: 1 Mo, was followed by a slower reaction which probably gave higher complexes. In the reactions with o-aminophenol and 2,2′-bipyridyl, complexes of stoichiometry 1 ligand: 1 Mo and 1 ligand: 2 Mo, respectively, were formed in solutions. The following complexes have been isolated: Mo2O4(dtc)2, Mo2O3(dtc)4 (dtc=diethyldithiocarbamate), MoOCl3. phen (phen=1,10-phenanthroline), and Mo2O3Cl4(bpy)2 (bpy=2,2′-bipyridyl). The infrared and electronic spectra of the complexes and their probable structures are given. The relative ease of replacement of ligands from complex (I) has been discussed.

Abstract: This work reports the ligational behavior of the neutral bidentate chelating molecule 2-(3,5-dimethyl pyrazol-1-yl) benzothiazole towards the oxomolybdenum(V) center. Both mononuclear complexes of the type (MoOX3L)-O-V and binuclear complexes of the formula (Mo2O4X2L2)-O-V (where X = Cl, Br) are isolated in the solid state. The complexes are characterized by elemental analyses, various spectroscopic techniques (UV-Vis IR), magnetic susceptibility measurement at room temperature, and cyclic voltammetry for their redox behavior at a platinum electrode in CH3CN. The mononuclear complexes (MoOX3L)-O-V are found to be paramagnetic while the binuclear complexes Mo2O4X2L2 are diamagnetic. Crystal and molecular structure of the ligand and the dioxomolybdenum complex (MoO2Br2L)-O-VI (obtained from the complex MoOBr3L during crystallization) have been solved by single crystal X-ray diffraction technique. Relevant DFT calculations of the ligand and the complex (MoO2Br2L)-O-VI are also carried out.

Abstract: The extraction of iron(III) from aqueous solutions by di(2-ethylhexyl)phosphoric acid (DEHPA, HA) in hexane at constant ionic strength (0.5 M NaNO3), has been investigated under acidic conditions by means of metal distribution measurements. Iron(III) was extracted by ion-exchange reactions via the species: FeA3(HA)3, Fe2A3(HA)5 and Fe3A3(HA)3 in the organic phase. The corresponding stability constants were determined as: log β1 = 16.87, log β2 = 25.02 and log β3 = 18.39, respectively.