M.Akbar Ali

Synthesis and characterization of some new nickel(II), zinc(II) and cadmium(II) complexes of quadridentate SNNS ligands

Abstract Two new quadridentate Schiff base ligands formed from 2,5-hexanedione and S-alkyldithiocarbazic acids and their nickel(II), zinc(II) and cadmium(II) complexes having the general formula [M(SNNS)] (SNNS 2− is the dinegatively charged ligands) have been synthesized and characterized by elemental analysis and magnetic and spectroscopic methods. The Ni(SNNS) complexes are diamagnetic and square-planar. The Zn(SNNS) complexes are assigned with polymeric structures with mercapto sulphur-bridging. The Cd(SNNS) complexes presumably have polymeric structures.

Synthesis, characterization and fungitoxicities of metal chelates of a pentadentate N3S2 ligand

Abstract The Schiff base obtained by reaction of S-methyldithiocarbazate with 2,6-di-acetylpyridine behaves as a dinegatively charged pentadentate N 3 S 2 chelating agent producing stable crystalline complexes of the general formula, M(SNNNS) (where M = Ni, Cu, Co, Zn and Cd; SNNNS = the dinegative anion of the Schiff base). The complex Fe(SNNNS)C1 was also isolated. Conductivity data and magnetic and spectroscopic evidence support a five-coordinate configuration for the M(SNNNS) complexes and an octahedral configuration for the Fe(SNNNS)Cl complex. Fungitoxicities of the Schiff base and its metal complexes against three plant pathogens viz. Alternaria solani, Curvularia geniculata and Colletotrichum capsici have been studied. The ligand and its complexes display marked antifungal activities against all the test fungi.

Four- and five-coordinate copper(II) complexes containing mixed ligands

Abstract New copper(II) complexes of general formula, Cu(ONS)B (ONS = the di-negatively charged Schiff base, S-benzyl-β-N-(2-hydroxyphenyl) methylendithiocarbazate; B = pyridine, 2,2′-dipyridyl or 1,10-phenanthroline) have been synthesized and characterised by magnetic and spectroscopic measurements. The complex, Cu(ONS)py is four-coordinate and square-planar. Magnetic and spectroscopic data support a five-coordinate, presumably, a trigonal-bipyramidal structure for the [Cu(ONS)dipy] and (Cu(ONS)phen] complexes

Transition metal complexes of furfural and benzil schiff bases derived from S-benzyldithiocarbazate

Abstract New nickel(II), copper(II), cobalt(III) and rohdium(III) complexes of two Schiff base ligands formed by condensation of furfural and benzil with S-benzyldithiocarbazate have been synthesized and characterized by elemental analysis and magnetic and spectroscopic measurements. The nickel(II) complexes, Ni(Nue5f8S)2 and Ni(Oue5f8Nue5f8S)2 (Nue5f8S and Oue5f8Nue5f8S stand for the uninegatively charged furfural and benzil Schiff bases, respectively) are square-planar and octahedral, respectively. The Cu(Nue5f8S)Cl complex is paramagnetic with a magnetic moment fo 1.73 B.M. A halogen-bridged dimeric structure is proposed for this complex. The copper(II) complex, Cu(Oue5f8Nue5f8S)Cl is diamagnetic, suggesting strong antiferromagnetic interactions between a pair of copper(II) ions in a thiolo sulphur-bridged dimeric or polymeric structure. Cobalt(II) ions are oxidized in the presence of the Schiff bases with the concomitant formation of cobalt(III) complexes of empirical formulae, Co(Nue5f8S)3, Co(Oue5f8Nue5f8S)2ClO4 and Co(Oue5f8Nue5f8S)2Cl, respectively, which are spin-paired and octahedral. The rhodium(III) complex of the furfural Schiff base, Rh(Nue5f8S)2Cl is tentatively assigned a halogen-bridged dimeric structre.

Metal complexes of some schiff bases derived from s-benzyldithiocarbazate

Abstract New metal complexes of Schiff base ligands derived from S-benzyldithiocarbazate have been prepared and characterized by elemental analysis and magnetic and spectroscopic measurements. In neutral or slightly acidic media, the Schiff bases formed from acetone, benzophenone, acetaldehyde and benzaldehyde behave as neutral [NS] bidentate chelating agents forming both bis- and tris-chelated nickel (II) complexes of general formula, Ni[NS] 2 X 2 (X = Cl − , NCS − ) and Ni [NS] 3 X 2 (X = Cl − , Br − and NO 3 − ), respectively, which are high-spin and octahedral. The complexes, Co[NS] 3 X 2 (X = Cl − or NO 3 − ) and Cu[NS] 2 (NO 3 ) 2 were also isolated. Magnetic and spectral evidence support an octahedral structure for the cobalt(II) complexes and a square-planar structure for the copper(II) complexes. In the presence of alkali the NS Schiff bases deprotonate yielding neutral complexes, Ni[NS − ] 2 which are diamagnetic and square-planar. The diacetyl Schiff base of S-benzyldithiocarbazate behaves as a dinegatively charged quadridentate ligand forming neutral 1:1 complexes with nickel and copper(II). Magnetic and spectral data are in accord with a square-planar structure for these complexes.

Synthesis and characterization of some metal complexes containing a quadridentate NSSN and a sexidentate ONSSNO ligand

Abstract New metal complexes of general formulae M(NSSN)X2 · xH2O (M = Ni, Cu; NSSN = quadridentate sulphur-nitrogen ligand; X = Cl, Br, NCS or I; x = 0 or 2) and M(ONSSNO) [M = Ni, Cu, Zn, Cd; ONSSNO2− = anion of sexidentate ligand formed from salicylaldehyde and α,α′-xylene-bis(N-methyldithiocarbazate)] have been prepared and characterized by conductance, magnetic and spectroscopic measurements. The nickel(II) complexes of both the ligands are high-spin and octahedral. Tetragonally distorted octahedral structures are assigned to the copper(II) complexes. In the presence of the sexidentate ligand, cobalt(II) is readily air-oxidized to form a cobalt(III) complex, Co(ONSSNO)Cl, which is spin-paired and octahedral.

The preparation and characterization of some nickel(II) and copper(II) complexes of ons ligands

Abstract New nickel(II) and copper(II) complexes of four Schiff base ligands formed from benzoylacetone and 2-hydroxynaphthaldehyde with S-alkyl esters of dithiocarbazic acid have been prepared and characterized by IR, NMR, ESR and electronic spectroscopic techniques. The Schiff bases yield neutral 1 : 1 complexes of general formula M(ONS) (ONS2− = dinegatively charged anions of the Schiff base ligands; M = Ni, Cu). Magnetic and spectral evidence support a dimeric structure for these complexes. The complexes, M(ONS)B (B = py, dipy, phen), were also prepared. The complexes, M(ONS)py, are square-planar but electronic and ESR spectroscopic data support a five-coordinate geometry for the Cu(ONS)B (B = dipy, phen) complexes. Based on spectroscopic and magnetic data, a thiolato, sulphur-bridged, octahedral structure is assigned to the Ni(ONS)B (B = dipy, phen) complexes.

Metal ion induced rearrangements of 1,3,4-thiadiazolidine-2-thiones—I. The rearrangements of 3-methyl-5-(2-pyridyl)- and 3-methyl-5-(6-methylpyrid-2-yl)-1,3,4-thiadiazolidine-2-thiones with nickel(II), zinc(II) and cadmium(II) ions

Abstract 3-Methyl-5-(2-pyridyl)- and 3-methyl-5-(6-methylpyrid-2-yl)-1,3,4-thiadiazolidine-2-thiones have been synthesized and characterized by spectroscopic techniques. The thiadiazolidine-2-thiones react with nickel(II), zinc(II) and cadmium(II) acetates producing intensely-coloured, stable metal complexes. Conductance, magnetic and spectroscopic evidences indicate that the rearrangement of the thiadiazolidine-2-thiones to the corresponding Schiff bases occurs. The complexes have been characterized by magnetic and spectroscopic techniques.