S. A. A. Zaidi

Transition metal complexes of hydrotris(imidazolyl)borate anion

The preparation and characterization of the ligand potassium hydrotris(imidazolyl)borate and some of its complexes with transition metals is reported. These complexes have apparently an octahedral structure except the Cu(II) complex which seems to have a square planar geometry. The values of the ligand field parameters 10Dq, B and β have been evaluated for most of these complexes.

Tetrakis(1-indazolyl)borate Complexes with Transition Metals

Abstract A novel ligand, potassium tetrakis(1-indazolyl)borate has been synthesized from potassium borohydride and indazole at 215°C in a closed assembly. Complexes of this newly synthesized chelate have been prepared with Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) halides. These have been characterized by elemental analysis, IR, reflectance spectra, room temperature magnetic susceptibility- and conductance measurements. Except for the Cu(II) complex, these complexes appear to have an octahedral structure. The molar conductance value of 10−3M solutions of all complexes, except the Ni(II) complex, support nonionic species. B and 10 Dq values have been calculated where appropriate.

Characterization and toxicity of lanthanide complexes with nitrogen- and sulphur-containing Schiff bases

Abstract La(III), Ce(III), Pr(III), Nd(III), Gd(III), Dy(III), Ho(III) and Er(III) complexes of Schiff bases derived from sulphamethoxazole and salicylaldehyde (I), and thiophene-2-aldehyde (II) have been characterized on the basis of IR, NMR, UV-Vis spectroscopy, elemental analysis, conductance measurements and molecular weight determinations. The Schiff bases act as monobasic bidentate ligands, rendering the metal eight-coordinated. The equilibrium constants have been studied in solution at 25, 30 and 35 °C. The nephelauxetic effect (1 - β), bonding parameter (β), b1/2 and Sinha covalency parameter (δ) have been calculated. The positive values indicate the covalent nature of the metal-ligand bond. The covalent nature of the complexes is also supported by molar conductance measurements. The toxicities of the Schiff bases and their complexes were evaluated against insects. The LD50 value for cockroaches and percent growth inhibition of the fungi show greater efficacy for the complexes than the Schiff bases.

Piperazine Bis(dithiocarbamate) and Diethyl Dithiocarbamate Complexes of Some Triorganotin Compounds

Abstract Piperazine bis(dithiocarbamate) (pzbisdtc) and diethyl dithiocarbamate (ET2dtc) complexes of R3SnX (where R = phenyl, methyl, butyl; X = acetate, chloride) have been synthesized and characterized by elemental analysis and I.R. spectral studies. The complexes formed have a 1:1 (M:L) ratio except (Ph3Sn)2Pz bisdtc. The compounds are thermally stable and insensitive to moisture. In all the cases the dithiocarbamato moiety has been found to be symmetrically coordinated to the tin atom.

Coordination properties of new indazole derivatives

SummaryThe bidentate nitrogen donor ligands 2-(1-indazolyl) pyridine and 2-(1-indazolyl) pyrimidine have been synthesised. Their complexes with MnII, CoII, NiII, CuII and ZnII have been prepared and characterised by elemental analysis, i.r., u.v. spectra and magnetic susceptibility measurements. The complexes are nonelectrolytes and have magnetic moments consistent with an octahedral environment.

Synthesis, vibrational spectra and stereochemistry of lanthanide tris(chlorosulphates), Ln(SO3Cl)3 (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er)

Abstract -Lanthanide(III) chlorosulphates, Ln(SO3Cl)3 (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) have been synthesized by solvolytic reaction of chlorosulphuric acid on the corresponding benzoates. The low conductivity values and the IR spectra of these compounds suggest a cation-anion interaction leading to covalent bonding. The bands observed in the reflectance spectra and the values of magnetic moments may indicate a coordination number of 6 for these metals, with bidentate chlorosulphate groups.

Organotellurium Derivatives. Syntheses and Characterization of Dimethyl and Diethyl Telluriumdichlorosulphates [R2Te(SO3Cl)2]

Abstract Dimethyl and diethyl telluriumdichlorosulphates have been isolated in the form of dark brown colored crystalline solids utilizing the solvolytic reactions of the corresponding di-iodides with chlorosulphuric acid. The electrical conductivity and IR spectroscopic studies confirm that these compounds are non-ionic and the mode of linking of the chlorosulphate group to the tellurium atom is covalent, resulting in a reduced Cs symmetry for the chlorosulphate group. The PMR spectral study indicates that the corresponding methyl and ethyl protons of these molecules are deshielded which is consistent with the lowering of the non-bonded electron density at tellurium atom due to its drainage towards the chlorosulphate group.

Coordinating Properties of Chlorosulphate Ion; Synthesis and Characterization of Mn (II), Co (II), Ni(II) and Cu(II) Bis-(Chlorosulphates) and Their Complexes with Nitrogen-Containing Bases

Abstract Chlorosulphates of the divalent transition metals Mn(II), Co(II), Ni(II) and CU(II) have been prepared and characterized. The electrical conductivities and i.r. spectral data indicate a considerable extent of cation-anion interaction and the anion is bonded in a tridentate manner such that it has a reduced Cs symmetry in the molecule. The magnetic susceptibility measurements and the ligand field spectroscopic studies are consistent with the octahedral geometry for these salts and indicate the presence of some covalent bonding between the chlorosulphate ion and the metal ion. However, a tetragonal distortion in the geometry has been indicated for the Ni(II) salt. The coordination compounds of the type ML4(SO3Cl)2[L=acetonitrile, pyridine, pyridine N-oxide] and ML2(SO3Cl)2 [L = 2,2′bipyridine, acridine] have also been prepared and characterized. The i.r. and ligand field spectroscopic studies and magnetic susceptibility measurements indicate the presence of a strong interaction between the anion an...

Synthesis and Characterization of Homocystine Chelates with a Few Transition Metal Ions

Abstract Complexes of homocystine, [-SCH2CH2CH(NH2)COOH]2, have been prepared with Cr(II), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) chlorides. They have been characterized by elemental analyses, diffuse reflectance spectra and magnetic susceptibility measurements. The elemental analyses indicates a 1:1 metal: ligand ratio. The divalent metal ions are coordinated through all the donor sites of the amino acid while trivalent iron seems to be coordinated only through nitrogen and oxygen with bridging chlorine atoms. The spectral and magnetic data suggest an octahedral metal environment in all these complexes except for Zn(II) and Cd(II).

A Study of Transition Metal Complexes of 2-Thiobarbituric Acid

Abstract A few transition metal complexes of 2-thiobarbituric acid (TBA) have been synthesized and characterized by chemical analyses, i.r.- and reflectance spectroscopic studies and magnetic susceptibility measurements. On the basis of these studies Cu(II), Cd(II) and Pd(II) complexes have been proposed to have square-planar geometry While those of Mn(II), Fe(III), Co(II), Ru(III), Rh(III), Ir(III) and Pt(IV) were found to be octahedral. Mn(II), Cu(II), Co(II) and Fe(III) complexes are magnetically subnormal. TBA has been found to act as a bidentate or quadridentate ligand. The sulphur atom in no case has been claimed as a coordination site. Metal ligand stretching frequencies occur in the range 175–270 cm−1 for first row transition metals and Cd(II), which follow the Irwing-Williams sequence of metal ions: