The preparation and characterization of some new nickel(II), copper(II), zinc(II) and cadmium(II) complexes of the pyrrole-2-carboxaldehyde Schiff bases ofS-alkyl esters of dithiocarbazic acid

Summary New complexes of general formulae [Ni(HL)₂], [ML]·H₂O and [Cu(HL)X] (H₂L = pyrrole-2-aldehyde Schiff bases ofS-methyl- andS-benzyldithiocarbazates; X = Cl or Br; M = Ni^II, Cu^II, Zn^II or Cd^II) were prepared and characterized by a variety of physicochemical techniques. The Schiff bases coordinate as NS bidentate chelating agents in [Ni(HL)₂] and [Cu(HL)X], and as tridentate NNS chelates in [ML] (M = Ni^II, Cu^II, Zn^II or Cd^II). Both the [Ni(HL)₂] and [NiL] complexes are diamagnetic and square-planar. Based on magnetic and spectroscopic evidence, thiolate sulphur-bridged dimeric square-planar structures are assigned to the [Cu(HL)X] and [ML] (M = Ni^II or Cu^II) complexes. The complexes ML (M = Zn^II or Cd^II) are polymeric and octahedral.     

N-Phthaloylglycinate ternary complexes with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) metal ions and aromatic mono,bi and tridentate amines

Complexes of N-phthaloylglycinate (N-phthgly) and Co^II, Ni^II, Cu^II, Zn^II and Cd^II containing imidazole (imi), N-methylimidazole (mimi), 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen), and tridentate amines such as 2,2,2-terpyridine (terpy) and 2,4,6-(2-pyridyl)s-triazine (tptz), were prepared and characterized by conventional methods, i.r. spectra and by thermogravimetric analysis. For imi and mimi ternary complexes, the general formula [M(imi/mimi)₂(N-phthgly)₂]·nH₂O, where M = Co^II, Ni^II, Cu^II and Zn^II applies. For Cd^II ternary complexes with imi, [Cd(imi)₃(N-phthgly)₂]·2H₂O applies. For the bi and tridentate ligands, ternary complexes of the formula [M(L)(N-phthgly)₂]·nH₂O were obtained, where M = Co^II, Ni^II, Cu^II and Zn^II; L = bipy, phen, tptz and terpy. In all complexes, N-phthgly acts as a monodentate ligand, coordinating metal ions through the carboxylate oxygen, except for the ternary complexes of Co^II, Ni^II and Cu^II with mimi and Cu^II and Zn^II with imi, where the N-phthgly acts as a bidentate ligand, coordinating the metal ions through both carboxylate oxygen atoms.     

Synthesis and chemical characterization of biologically important complexes of vanillin thiosemicarbazone with manganese(II), iron(II), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and mercury(II)

Summary Vanillin thiosemicarbazone (VTSC) has been used to isolate the complexes of the types [M(VTSC)₂(H₂O)₂]X₂ (M=Mn^II, Fe^II, Co^II, or Ni^II and X=Cl) and [M(VTSC)X₂]H₂O (M=Cu^II, Zn^II, Cd^II or Hg^II and X=Cl). Probable structures of these complexes are suggested on the basis of elemental analysis, molar conductance, magnetic moment and electronic and i.r. spectral data. The fungicidal activity of VTSC and the isolated complexes has been evaluated on pathogenic fungi,Alternaria (Sp.),Paecilomyces (Sp.) andPestalotia (Sp.).On leave from the University of Myosore.     

Complex formation equilibria between mercury(II) complexes of pencillamine and glutathione and transition metal ions

Summary The interaction between Hg^II complexes of the thiols pencillamine and glutathione and some transition metal ions has been investigated potentiometrically. Mixedmetal complexes of the forms Hg(ps)₂M and Hg(gs)₂M (where M=Co or Ni), were detected. The complexes formed between glutathione disulphide with bivalent metal ions Zn^II, Ni^II, Co^II and Cd^II have also been studied. Zn^II and Ni^II form the complexes M(gssg)H and M(gssg), while Co^II and Cd^II form only the fully deprotonated complex M(gssg). The formation constants of the complexes were determined at 25°C and I=0.1 M (NaNO₃). The concentration distribution of various complex species as a function of pH was evaluated.     

Complexes of 2-(2-hydroxyacetophenone)imino-5-(p-anisyl)-1,3,4-oxadiazole with some bivalent metals ions

Summary The metal complexes of the type [M(SB)₂(H₂O)₂] and [M(SB)₂][where M = Mn^II, Co^II, Ni^II or Cu^II, M = Zn^II Cd^II, Hg^II and Pb^II and SBH = 2-(2-hydroxyacetophenone)imino-5-(p-anisyl)-1,3,4-oxadiazole] have been prepared and characterised by elemental analyses, thermal analyses, magnetic measurements, electronic and infrared spectral studies. The complexes [M(SB)₂(H₂O)₂] possess octahedral structures, whereas complexes [M(SB)₂] are tetrahedral. The crystal field parameters of the Co^II and Ni^II complexes are also calculated.     

Synthesis and structural characterization of 3d-metal complexes of pyridine-4-carboxaldehyde thionicotinoyl hydrazone

Summary Pyridine-4-carboxaldehyde thionicotinoyl hydrazone (4-PTNH) forms 1:1 adducts with metal(II) halides and 1:2 complexes (metal to ligand) with metal(II) thiocyanates. Magnetic and spectral studies indicate polymeric octahedral geometry for M(4-PTNH)X₂ (M=Co^II or Cu^II, X=Cl; M=Ni^II, X=Cl, Br or I), five coordinate geometry for Co(4-PTNH)X₂ (X=Br or I) and octahederal geometry for [M(4-PTNH)₂(NCS)₂] (M=Co^II or Ni^II). I.r. spectral studies show that 4-PTNH acts as a neutral bidentate ligand in all the complexes, the bonding sites being the thione sulphur and azomethine nitrogen.     

Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

Summary The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me₂CO solution of the diazole to yield complexes of the general formula: [M(Iz)₂] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)₂] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PrⁱIz)₂] (where M = Co, Ni, Cu, Zn; PrⁱIz = 2-isopropylimidazolate); [M(pyIz)_n] (where M = Co^III, Cu^II, Zn^II; pyIz = 2-(2-pyridyl)imidazolate); [M(Pz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; Pz = pyrazolate); [M(ClPz)_n] and [M(IPz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me₂Pz)_n] (where M = Co^II, Cu^I, Zn^II; Me₂Pz = 3,5-dimethylpyrazolate) and [M(BrMe₂Pz)_n] (where M = Co^II, Ni^II, Cu^I, Zn^II; BrMe₂Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S= ) model for an infinite one-dimensional linear chain, yielding best fit values of J=–62––65cm^–1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S= ) model with J=–4.62––11.7cm^–1 andg = 2.06–2.49.     

The synthesis,characterization and spectral studies of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl) methyl]amino}butyl) N′,N′-dihydroxyethanediimidamide

Co^II, Ni^II, Cu^II, Zn^II and Cd^II complexes of N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]amino}butyl)N′,N′-dihydroxyethanediimidamide (LH₂) were synthesized and characterized by elemental analyses, IR, ¹H- and ¹³C-NMR spectra, electronic spectra, magnetic susceptibility measurements, conductivity measurements and thermogravimetric analyses (TGA). The Co^II, Ni^II and Cu^II complexes of LH₂ were synthesized with 1?:?2 metal ligand stoichiometry. Zn^II and Cd^II complexes with LH₂ have a metal ligand ratio of 1?:?1. The reaction of LH₂ with Co^II, Ni^II, Cu^II, Zn^II and Cd^II chloride give complexes Ni(LH)₂, Cu(LH)₂, Zn(LH₂)(Cl)₂, Cd(LH₂)(Cl)₂, respectively.     

Isonitrosoacetylacetone dithiosemicarbazone complexes of some first row transition metals

Summary Complexes of the potentially tetradentate ligand isonitroso-acetylacetone dithiosemicarbazone (inbtH₂) of formulae [Ti(inbtH₂)Cl₂]Cl₂, [M(inbt)], where M = V^IV O, Mn^II, Ni^II or Zn^II, [M(inbtH₂)X₂], where M = Co^II and X = Cl, or M = Ni^II and X = Cl, Br or I, and [M(inbtH₂)Cl₂]Cl, where M = Cr^III or Fe^III, have been prepared and characterized by physico-chemical and spectroscopic methods. In all the compounds the metal is coordinated by the thiocarbonyl sulphur and imine nitrogen, as revealed by i.r. studies. The n.m.r. spectra of the complexes of Ni^II and Zn^II confirm coordination through nitrogen. Possible structures for the complexes are proposed. The Mössbauer spectrum of the Fe^III complex is discussed.     

Potentiometric determination of the formation constants for complexes of 3,2′,2″-triaminopropyldiethylamine with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II)

The tripodal tetraamine ligand N{(CH₂)₃NH₂}{(CH₂)₂NH₂}₂ (pee), has been investigated as an asymmetrical tetraamine chelating agent for Co^II, Ni^II, Cu^II, Zn^II and Cd^II. The protonation constants for this ligand and the formation constants for its complexes have been determined potentiometrically in 0.1 M KCl at 25 °C. The successive protonation constants (log K _n ) are: 10.22, 9.51, 8.78 and 1.60 (n = 1–4). One complex with formula M(pee)²⁺ (M = Co, Ni, Cu, Zn and Cd) is common to all five metal ions and the formation constant (log _ML) is: 12.15, 14.17, 16.55, 13.35 or 9.74, respectively. In addition to the simple complexes, Co^II, Cu^II and Zn^II also give hydroxo complexes, and Cu^II and Ni^II give complexes with monoprotonated pee. [Zn(pee)](ClO₄)₂ and [Cd(pee)Cl](ClO₄) complexes were isolated and are believed to have tetrahedral and trigonal-bipyramidal structures, respectively.     

Transition metal complexes with thiosemicarbazide-based ligands,Part II,Synthesis and characterisation of nickel(II), cobalt(II), manganese(II) and zinc(II) complexes with the pentadentate ligand, 2,6-diacetylpyridine bis(S-methylisothiosemicarbazone)

Summary The reaction of warm alcoholic solutions of acetates of Co^II, Mn^II, Zn^II and Ni^II with 2, 6-diacetylpyridine andS-methylisothiosemicarbazide hydrogen iodide yielded the complexes: [Co(H₂L)I₂]·H₂O, [Mn(H₂L)(MeOH)₂]I₂, [Zn(H₂L)(MeOH)I]I and [Ni(HL)]I, (H₂L=the pentadentate pentaaza-ligand 2, 6-diacetylpyridine bis(S-methylisothiosemicarbazone)). The reaction of methanolic solutions of [Ni(HL)]I and NH₄NCS or LiOAc.2H₂O, give [Ni(HL)]NCS and NiL, respectively. For the complexes of Co^II, Mn^II and Zn^II, a pentagonal bipyramidal configuration is proposed, with H₂L in the equatorial plane and two unidentate ligands (I and/or MeOH) in the axial positions. The complexes [Ni(HL)]X (X=I or NCS) and NiL probably have monomeric five- and dimeric six-coordinate structures, respectively, in which only the chelate ligand is involved in coordination.     

Metal(II) complexes and metal(II) salts ofN-carbamoylpyrazole: N,O and N,N coordination

Summary Several new coordination compounds are reported withN-carbamoylpyrazole (Hcpz) as the ligand;viz. M(cpz)₂ where M = Cu^II and Ni^II; M(Hcpz)Cl₂ where M = Mn^II, Co^II, Cu^II, Zn^II and Cd^II; M(Hcpz)₂Cl₂ Where M = Fe^II, Co^II and Ni^II: M(Hcpz)₃(BF₄)₂ where M = Fe^II, Co^II, Ni^II, Zn^II and Cd^II; and Cu(Hcpz)₂(BF₄)₂. In the salts, Hcpz is coordinated through the nitrogen atoms of the pyrazole ring and the nitrogen atom of the carbamoyl group. In the Hcpz complexes, coordination takes place through the nitrogen atom of the pyrazole ring and the oxygen atom of the carbamoyl group.     

Synthesis and antibacterial activity of metal complexes of ciprofloxacin

The interactions of ciprofloxacin (HCipro) with transition metals have been investigated. Two types of complexes, [M(Cipro)(OAc)(H₂O)₂] · 3H₂O (M = Mn^II, Co^II, Cu^II or Cd^II) and [M(Cipro)(OAc)] · 6H₂O (M = Ni^II or Zn^II), were obtained and characterized by physicochemical and spectroscopic methods. The i.r. spectra of the complexes suggest that the ciprofloxacin behaves as a monoanionic bidentate ligand. In vitro antibacterial activities of the HCipro and the complexes were tested.     

Synthesis and spectroscopic studies on 3-isonicotinamidorhodanine complexes of some bivalent metal ions

Summary 3-Isonicotinamido-rhodanine (HINRd) reacts with metal ions to yield complexes of the types M(INRd)OH·nH₂O (where M=Co^II, Ni^II, Zn^II or Cd^II and n=1 or 2), Cu(HINRd)X·2H₂O (where X=Cl or Br), Pd(HINRd)Cl₂ and Cd(HINRd)X₂·H₂O (where X=Cl or Br), depending on the metal salt used and the reaction conditions. The metal complexes have been characterized by elemental analysis, molar conductivities, molecular weights, magnetic susceptibility, visible, and i.r. studies. The i.r. spectra show that HINRd binds in a bidentate or monodentate manner. The spectral and magnetic studies suggest a tetrahedral arrangement for Co^II, octahedral for Ni^II and square-planar for Pd^II. HINRd behaves as a reducing agent towards Cu^II chloride or bromide forming diamagnetic Cu^I complexes.     

Synthesis, Characterization and Antibacterial Activity of Some Transition Metal cis-3,7-dimethyl-2,6-octadiensemicarbazone Complexes

The synthesis and characterization of some transition metal cis-3,7-dimethyl-2,6-octadiensemicarbazone (CDOSC) complexes are reported. The ligand CDOSC yields: [ML₂ Cl₂] and [ML₂ Cl₂] Cl type complexes, where M = Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II, Zn^II, Cd^II and Hg^II, L = CDOSC. Structures of the complexes were determined using elemental analysis, molar conductivity, magnetic measurements, i.r. and electronic, as well as n.m.r spectra. CDOSC acts as a bidentate ligand in all the complexes. All the newly synthesized metal complexes, as well as the ligand, were screened for their antibacterial activity. All the complexes exhibit strong inhibitory action against Gram (+) bacteria Staphylococcus aureus and Gram (−) bacteria Escherichia coli. The antibacterial activities of the complexes are stronger than those of the ligand CDOSC itself.     

On the different coordination of Ni, Zn and Cd cations in their model Schiff base complexes - Single crystal X-ray and solid state NMR studies

Three model metal complexes: Ni(NCS)L, Zn₂(NCS)₂L₂ and Cd₂(NCS)₂L₂, consisting of the SCN⁻ anion(s) and L = 2-[(2-dimethylaminoethylimino)-methyl]-phenolate, have been studied by X-ray diffraction and solid state NMR spectroscopy. The metal cations in these complexes have different coordination modes: Ni²⁺ is almost square-planar, the Zn²⁺ cation in Zn₂(NCS)₂L₂ is pentacoordinated, whereas Cd²⁺ is penta- and hexacoordinated in [Cd₂(NCS)₂L₂]. The different coordination of the metal cations influences the chemical shifts of the metal cations and also the nitrogen atoms. These chemical shifts can be correlated with the M-N and M-O bond lengths (M = Ni²⁺, Zn²⁺, Cd²⁺).     

Studies on the stereochemistry of diphenyl diketone monothio-semicarbazone and its transition metal complexes

Summary The stereochemistry and complexation behaviour of diphenyl diketone monothiosemicarbazone (DKTS) with Cu^II, Co^II, Ni^II, Cd^II, Zn^II, Pd^II, Pt^II, Ru^III, Rh^III and Ir^III have been investigated by means of chemical, magnetic and spectral (i.r., Raman, ¹H- and ¹³C-n.m.r. and electronic) studies. The ligand forms complexes of the M(DKTS)₂ type with Ni^II, Cu^II and Co^II having a distorted octahedral geometry. The absence of a v(M—X) band in the i.r. spectra, coupled with their 1:1 electrolytic conductances, suggests that Ru^III, Rh^III and Ir^III form octahedral complexes of the [M(DKTS)₂]Cl type. A four-coordinate structure involving bridging halides is proposed for the Zn^II, Cd^II, Pd^II and Pt^II complexes, which have relatively low v(M—X) vibration modes.     

Coordination compounds derived from transition metal salts and bis(3,5-dimethylpyrazolyl)methane

Summary The preparation of transition metal complexes containing the sterically hindered ligand, bis(3,5-dimethylpyrazolyl)methane (LL) is described. Compounds of formula M(LL)X₂ (M = Co^II, Ni^II or Zn^II and X = Cl^– or Br^–) or M(LL)₂X₂ (M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II, Zn^II or Cd^II and X = ClO ₄ ^– ; M = Co^II, Ni^II, Cu^II or Zn^II and X = NO ₃ ^– ; M = Ni^II or Cu^II and X = Cl^– or Br^–) have been isolated. In addition, an apparently trimeric Cu₃(LL)₄Cl₆ · EtOH compound is reported. For Ni(LL)Cl₂ a five-coordinated chloro-bridged dimer is found. The perchlorato compounds, M(LL)₂(ClO₄)₂, appear to have one bidentate ClO ₄ ^– and one ionic ClO ₄ ^– group. The M(LL)₂ species appears to occur either in octahedral geometry, leaving twocis-positions free, or in a tetrahedral geometry without space for other ligands, and probably also in a five-coordinate geometry with one free ligand position.Structural conclusions are drawn from i.r., far-i.r. and ligand-field spectra, x-ray powder patterns, magnetic susceptibility data, e.s.r. spectra and conductivity data.     

2-Aminoacetophenone-2-thenoylhydrazone complexes of bivalent 3d metal ions

Summary 2-Aminoacetophenone-2-thenoylhydrazone, Haath, C₄H₃SC(O)NHN=C(Me)C₆H₄NH₂-o, forms complexes with metal(II) salts of empirical compositions [VO(Haath)₂SO₄], [M(Haath)₂Cl₂] [M=Co^II, Ni^II, Cu^II or Zn^II] and [M(aath)₂] [M=V^IVO, Co^II, Ni^II, Cu^II or Zn^II] which have been characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, e.s.r., i.r. and n.m.r. (¹H and¹³C) spectral studies. X-ray and electron diffraction patterns have been obtained in order to elucidate the structure of the Cu^II complexes. Photoacoustic spectra of powder Ni^II complexes have been recorded and interpreted in the light of u.v./vis. spectra.     

Metal complexes of 2-acetylpyridine N(4)-dihexyl- and N(4)-dicyclohexylthiosemicarbazones

Summary 2-Acetylpyridine N(4)-dihexyl- and N(4)-dicyclohexylthiosemicarbazone, HAc4DHex and HAc4DCHex, respectively, and Fe^III, Co^II, Co^III, Ni^II, Cu^II and Zn^II complexes have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. For many of the complexes, loss of the N(2)H hydrogen occurs, and the ligands coordinate to the metal centres as NNS monoanionic, tridentate ligands, e.g., [M(NNS)X] (M = Co^II, Ni^II, Cu^II, NNS = Ac4DHex or Ac4DCHex and X = Cl or Br), [Fe(NNS)₂]ClO₄, [Co(NNS)₂]BF₄, [Cu(NNS)NO₃] and [Zn(NNS)OAc]. Zn^II ion is also chelated by neutral ligands in [Zn(HNNS)X₂] (X = Cl, Br). In addition, [Ni(Ac4DHex)-(HAc4DHex)]X (X = BF₄, ClO₄) and [Ni(HAc4DCHex)₂]-(BF₄)₂ are reported where the neutral thiosemicarbazone is coordinated via the pyridyl nitrogen, azomethine nitrogen and thione sulfur. Crystal structure determinations of HAc4DCHex and [Cu(Ac4DHex)Br] show the former to contain the bifurcated hydrogen bonded form and the latter to be planar with no significant interaction between neighbouring centres.