H.K. Saha

Abstract: 1,10 Phenanthrolinium oxopentachloro molybdate(V), PhenH 2 [MoOCl 5 ] has been isolated as yellowish-green solid and from this salt the non-electrolytic paramagnetic complexes MoOCl 3 ·phen have been prepared in three different isometric (colored reddish-pink, pale brown and green) forms by dehydrohalogenation in suitable solvent and solid state reaction. Hydrolysis of the parent salt yielded the diamagnetic complex, Mo 2 O 4 Cl 2 (phen) 2 as brownish red solid. All these products and the parent salt have been shown to be interconvertible and the probable constitution of expected cis-trans isomers of MoOCl 3 ·phen has also been discussed. All these compounds have been studied by various physicochemical methods and it has been shown that the oxometal entity MoO 3+ remains intact under various chemical environments.

Abstract: The synthesis and structure elucidation of the dimeric form of molybdenum(IV) oxo-complexes with N-alkylphenothiazines as ligands have been studied. These complexes were identified by IR and electronic spectra, magnetic susceptibility, DTA, TGA, conductometric and analytical data. These results permit us to assign the formula Mo2O4(L)2(H2O)2 (where L = N-alkylphenothiazine). Some interactions of these complexes with biologically important compounds like L -cysteine and histidine and potential ligands such as 1,10-phenanthroline and 2,2′-bipyridyl have been reported.

Abstract: Compounds of the type {VOF3(AA)} (AA = phen, bpyO2), {VO2F(AA)} (AA = phen, bpy) and {VOF3L2} (L = pyO, picO) are the first examples of molecular derivatives of oxofluorovanadium(V) with organic ligands. They were characterised by their conductivity, infrared, visible and Debye-Scherrer spectra and magnetic susceptibility. The properties of the complexes {VOF3(AA)} and {VOF3L2} are consistent with an octahedral structure. The infrared spectra of the three compounds {VO2F(AA)} show two strong absorptions (in the 800–950 cm−1 region) which are likely to arise from vs and vas(VO2). The results of a single crystal X-ray diffraction study for one form of {VO2F(bpy)} (cis VO2 group, vanadium penta-coordinated with a weak sixth bond corresponding to dimers with bridge) seem to be valid for the two others.

Abstract: Mixed chelate complexes of identical composition of the type (NH4)2[UO2(L)2B] and (NH4)2[UO2(L)2X2] where L = anion of cupferron, B  CO″3, C2O″4 and X  F′, Cl′ have been prepared from different starting materials Both the fluoro- and chloro-complexes (NH4)2[UO2(L)2X2] have been isolated in two different forms (one orange-yellow and one yellow) by different methods Yellow forms of (NH4)2[UO2(L)2X2] undergo conversion to the corresponding orange-yellow forms under suitable conditions All these complexes have been thoroughly characterised through elemental analysis, conductance data, X-ray, IR, electronic, NMR spectra as well as thermogravimetric and differential thermal analyses Possibility of the complex (NH4)2[UO2(L)2X2] to exist in two geometrical isomeric forms has been indicated The orange red complex cis-[UO2(L)2(H2O)2] on being refluxed with acetone, changed to a yellow complex, almost insoluble in most of the common organic solvents Various physico-chemical studies indicate it to be a hydroxybridged dinuclear complex H[(UO2)2(L)4OH(H2O)2] The ν3-values (cm−1) of UO22+-entity from IR-spectra have been used to calculate the force constant, FUO in mdynes/A and the bond length RUO in A of the UO bond Using ν3of the UO22+-entity as a molecular probe, the inorganic ligands and acid residues like F′, Cl′, CO″3 and CO″4 have been arranged in a series, which is similar to the mutual displacement series of one ligand by another in the uranyl compounds