Spectral and magnetic studies of tin(IV) complexes with nickel(II) thiocarbohydrazones

Tin(IV) chloride derivatives of nickel(II) thiocarbohydrazones were obtained by reacting tin(IV) chloride with nickel(II) thiocarbohydrazones in chloroform medium. All the complexes are greenish coloured solids and appear to be non-electrolytes in DMF. Elemental analyses conform to the 1:1 stoichiometry. Magnetic, electronic and IR spectral information suggest that square planar nickel(II) thiocarbohydrazones have changed their configuration to octahedral as a result of reaction with tin (IV) chloride.     

Preconcentration of cadmium, cobalt, copper, nickel and zinc by solvent extraction into methyl isobutyl ketone with 1,5-bis [1-(2-pyridyl) ethylidene] thiocarbonohydrazide and 1,5-bis [phenyl-(2-pyridyl) methylene] thiocarbonohydrazide

The synthesis, physicochemical properties and interactions of two new thiocarbohydrazones, namely 1,5-bis[1-(2-pyridyl) ethylidene] thiocarbonohydrazide (APTH) and 1,5-bis[phenyl-(2-pyridyl) methylene] thiocarbonohydrazide (BPTH) have been studied as well as the use of both compounds as extracting reagents. These thiocarbohydrazones form yellow complexes with bivalent metal ions, and these are extractable into methyl isobutyl ketone. Conditions for quantitative extraction of Cd(II), Co(II), Cu(II), Ni(II) and Zn(II) are established from a critical study of the effect of pH, shaking time, reagent concentration in the organic phase, ionic strength and volume ratio of aqueous to organic phase.     

Spectral and magnetic studies on manganese(II), cobalt(II) and nickel(II) complexes with Schiff bases

Mn(II), Co(II) and Ni(II) complexes of 2-methylcyclohexanone thiosemicarbazone(MCHTSC L(1)) and 2-methylcyclohexanone-(4)N-methyl-3-thiosemicarbazone (MCHMTSC L(2)), general composition [M(L)(2)X(2)] (where M = Mn(II), Co(II), Ni(II), L = L(1) or L(2) and X = Cl(-), NO(3)(-), and [(1/2)SO(4)(2-)) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements, UV-vis, IR, EPR, and mass spectral studies. Various physico-chemical techniques suggest an octahedral geometry for all the complexes.     

Convenient synthesis of 2-(2-pyridyl)-1, 3-diaminopropane,and its copper(II), nickel(II), and cobalt(III) complexes

Summary 2-(2-Pyridyl)-1, 3-propanediol was converted into the diacetate, which was then condensed with phthalimide. The product was hydrolyzed with hydrochloric acid to give 2-(2-pyridyl)-1, 3-diaminopropane. The free amine gave 12 complexes with copper(II), nickel(II), and cobalt(III), which were characterized spectroscopically and magnetically. Features of the amine as a ligand are discussed. A few related complexes were also studied.     

Spectral and magnetic behaviour of some nickel(II) and cobalt(II) complexes of triazene 1-oxides

Some new nickel(II) and cobalt(II) complexes of triazene 1-oxides derived from amino pyridines are reported. Experimental evidence shows that the nickel(II) complexes are planar in the solid state but exhibit a planar⇋pseudooctahedral equilibrium. The pseudooctahedral species for the (RPyCl)₂Ni complexes involves chloro coordination. In chloroform solution the equilibrium shifts substantially to the right compared to benzene solution for these complexes. In the corresponding cobalt(II) complexes, the chloro-coordination is complete and the complexes have a distorted octahedral symmetry in both solid and solution phases.     

Remarkably efficient hydrolysis of methylparathion catalyzed by [2-(2-pyridyl)phenyl-C,N]palladium(II) complexes

The reaction of the palladium(II) acetate derivative [Pd(NwedgeC)(OAc)]2 (NwedgeC = (NC5H4-2-C6H4(C2,N) or (2-(2-pyridyl)-phenyl-C,N)) with methylparathion and water in THF leads to the formation of [Pd(NwedgeC)(mu-SP(=O)(OCH3)2)]2 (1), which reacts with PPh3 in THF to afford mononuclear complex [Pd(NwedgeC)(SP(=O)(OCH3)2)(PPh3)] (2). Compounds 1 and 2 have been characterized by 1H, 13C, and 31P NMR spectroscopy; elemental analysis; and single-crystal X-ray diffraction. When dissolved in water, 1 serves as a precatalyst for the hydrolysis of methylparathion. Kinetic and spectroscopic studies suggest that compound 1 dissociates in aqueous solution to afford cationic diaqua complex [Pd(NwedgeC)(OH2)2]+ (A). At basic pH, A is converted into its deprotonated form [Pd(NwedgeC)(OH2)(OH)] (B), which dimerizes to afford a dinuclear complex, presumably [Pd(NwedgeC)(mu-OH)]2 (C). At pH 7, the reaction is first order in substrate and first order in palladium catalyst A, with k2 = 146 +/- 9 M(-1) s(-1) at 303 K. At more-basic pH, the reaction rate increases and shows an apparent half-order dependence in palladium catalyst. These observations suggest that the active form of the catalyst at basic pH is B, whose concentration is controlled by an equilibrium with inactive C. Analysis of the data obtained at pH 9 yields a dimer formation constant K(f) = [C]/[B]2 = (6.6 +/- 5.6) x 10(6) M(-1) and a second-order rate constant k2 of (8.6 +/- 3.6) x 10(3) M(-1) s(-1) at 298 K. The pH dependence of the reaction rate as well as a spectroscopic titration indicates that the pKa of A is in the 9.5-9.7 range. Determination of the activation parameters at both pH 7 and 9 suggests that catalysis occurs via an associative mechanism whose rate-determining step involves the substitution of a water ligand of A by a molecule of methylparathion at neutral pH and nucleophilic attack of the phosphorus center of methylparathion by a hydroxide ligand of B at basic pH.     

Experimental and theoretical studies on the complexes of [Pb(m)-pyridyl]- (m = 1-4)

The pyridyl-lead complexes [Pb(m)-C5H4N](-) (m = 1-4), which are produced from the reactions between lead clusters formed by laser ablation and the pyridine molecules seeded in argon carrier gas, are studied by photoelectron (PE) spectra and density functional theory. The adiabatic electron affinity (EA) of [Pb(m)C5H4N](-) is obtained from PE spectra at photon energies of 308 and 193 nm. Theoretical calculation is carried out to elucidate their structures and bonding modes. A variety of geometries for the isomers are optimized to search for the lowest-energy geometry. By comparing the theoretical results, including the EA and simulated density of state spectra, with the experimental determination, the lowest-energy structures for each species are obtained. The following analysis of the molecular orbital composition provides the evidence that the pyridyl binds on lead clusters through the Pb-C sigma bond. Moreover, there is an apparent spin-state transition from triplet state toward singlet state for the ground-state structure of [Pb(m)C5H4N](-) with an increase of lead cluster.     

Antioxidant activity of some N-heterocycles derived from 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene) hydrazinecarbothioamide

Efficient and convenient synthesis of coumarin derivatives was accomplished via reactions of 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide with some carbon electrophiles, e.g. maleic anhydride, dimethyl acetylenedicarboxylate, 1,2-dichloroethane, 3′-nitro-w-bromoacetophenone, N-(4-acetylphenyl)-2-chloroacetamide, ethyl cyanoacetate/3-chlorobenzaldehyde and acetylacetone to construct some N-heterocycles such as thiazolidine, thiazole, pyrimidine and pyrazolone derivatives. The structures of all synthesized products were substantiated from their analytical and spectral data. The antioxidant activities of the synthesized compounds were examined.     

Synthesis,spectroscopic studies and structures of square-planar nickel(II) and copper(II) complexes derived from 2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol

Two new nickel(II) [Ni(L)₂] and copper(II) [Cu(L)₂] complexes have been synthesized with bidentate NO donor Schiff base ligand (2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol) (HL) and both complexes Ni(L)₂ and Cu(L)₂ have been characterized by elemental analyses, IR, UV–vis, ¹H, ¹³C NMR, mass spectroscopy and room temperature magnetic susceptibility measurement. The tautomeric equilibria (phenol-imine, O–H?N and keto-amine, O?H–N forms) have been systemetically studied by using UV–vis absorption spectra for the ligand HL. The UV–vis spectra of this ligand HL were recorded and commented in polar, non-polar, acidic and basic media. The crystal structures of these complexes have also been determined by using X-ray crystallographic techniques. The complexes Ni(L)₂ and Cu(L)₂ crystallize in the monoclinic space group P2₁/n and P2₁/c with unit cell parameters: a = 10.4552(3) Å and 12.1667(4) Å, b = 8.0121(3) Å and 10.4792(3) Å, c = 13.9625(4) Å and 129.6616(3)Å, V = 1155.22(6) Å³ and 1155.22(6) Å³, D_x = 1.493 and 1.476 g cm^?3 and Z = 2 and 2, respectively. The crystal structures were solved by direct methods and refined by full-matrix least squares to a find R = 0.0377 and 0.0336 of for 2340 and 2402 observed reflections, respectively.