Synthesis and characterization of heterobimetallic Ni(II)–Zn(II) complexes from bis(2-hydroxy-1 -naphthaldehyde)succinoyldihydrazone

Monometallic zinc(II) and nickel(II) complexes, [Zn(H₂nsh)(H₂O)] (1) and [Ni(H₂nsh)(H₂O)₂] (2), have been synthesized in methanol by template method from bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone (H₄nsh). Reaction of monometallic complexes with alternate metal(II) acetates as a transmetallator in 1 : 3 molar ratio resulted in the formation of heterobimetallic complexes [NiZn(nsh)(A)₃] and [ZnNi(nsh)(A′)₂] (A = H₂O (3), py (4), 2-pic (5), 3-pic (6), 4-pic (7)), (A′ = H₂O (8), py (9), 2-pic (10), 3-pic (11), and 4-pic (12)). The complexes have been characterized by elemental analyzes, mass spectra, molar conductance, magnetic moments, electronic, EPR, and IR spectroscopies. All of the complexes are non-electrolytes. Monometallic zinc(II) is diamagnetic while monometallic nickel(II) complex and all heterobimetallic complexes are paramagnetic. The metal centers in heterobimetallic complexes are tethered by dihydrazone and naphthoxo bridging. Zinc(II) is square pyramidal; nickel(II) is six-coordinate distorted octahedral except [ZnNi(nsh)(A)₂], in which nickel(II) has square-pyramidal geometry. The displacement of metal center in monometallic complexes by metal ion has been observed in the resulting heterobimetallic complexes.     

Heterogeneous reactions of solid nickel(II) complexes,VI

The kinetics of the thermal decomposition of square-planar complexes of the type Ni(NCS)₂L₂ (L=α-picoline; 2,6-lutidine and quinoline) was studied by following the loss of weight and using the isothermal method, in the temperature range of 72–147°. The reaction order found wasn=2/3; this together with macroscopic observations indicates that it is the proper chemical process which is the controlling factor of the total decomposition rate. The values of the activation energies decrease in the following order: Ni(NCS)₂ Q₂ > Ni(NCS)₂(2,6-lut)₂ > Ni(NCS)₂(α-pic)₂; this points to the reaction course according to the associative activation. Except for Ni(NCS)₂Q₂,ΔH was found to be >E _a. This experimental result may be explained by a multi-step mechanism. Possible intermediates are discussed.     

Synthesis and spectral studies on heterobimetallic complexes of manganese and ruthenium derived from bis[N-(2-hydroxynaphthalen-1-yl)methylene]oxaloyldihydrazide

The complex [Mn(L)(H₂O)₂] [H₄L = bis[N-(2-hydroxynaphthalen-1-yl)methylene]-oxaloyldihydrazide] reacts with activated ruthenium(III) chloride in methanol in 1:1.2 M ratio under reflux resulting in heterobimetallic complex of the composition [Mn(L)(H₂O)₄RuCl₂]Cl. The complexes of the composition [Mn(L)(A)₄RuCl₂]Cl were obtained when the above reaction was carried out in presence of heterocyclic nitrogen bases(A) such as pyridine(py), 3-picoline(3-pic) and 4-picoline(4-pic). The molar conductance values for these complexes in DMF(N,N-dimethyl formamide) solution indicate their 1:1 electrolytic nature. Magnetic moment values suggest that these heterobimetallic complexes contain Mn(IV) and Ru(III) in the same structural unit. Electronic spectral studies suggest six coordinated metal ions in these complexes. IR spectra reveal that the H₄L ligand coordinates in its keto-form to Mn(IV) and Ru(III).     

Thermal investigation of some heterocyclic ligand complexes of tin(IV) in the solid state

1,10-phenanthroline (phen), 2,2′-bipyridyl (bipy), pyridine (py) and 4-picoline (4-pic) complexes of dibutyltindichloride (Bu₂SnCl₂) and dimethyltindichloride (Me₂SnCl₂) were synthesized. The complexes were characterized with the help of elemental analyses, IR spectra and thermal analyses. The complexes were found to have the compositions [Bu₂SnCl₂·phen], [Bu₂SnCl₂·bipy], [Me₂SnCl₂·phen], [Me₂SnCl₂·bipy], [Me₂SnCl₂·2py] and [Me₂SnCl₂·2(4-pic)]·H₂O. All these complex compounds appeared to posses octahedral structures. Thermodynamic parameters, such as activation energyE _a ^* enthalpy change ΔH and entropy change ΔS, for the dehydration and sublimation of the complexes were evaluated using some standard methods.     

Spectral and structural studies of nickel(II) complexes of salicylaldehyde 3-azacyclothiosemicarbazones

Mononuclear nickel(II) complexes with two ONS donor thiosemicarbazone ligands {salicylaldehyde 3-hexamethyleneiminyl thiosemicarbazone [H₂L¹] and salicylaldehyde 3-tetramethyleneiminyl thiosemicarbazone [H₂L²]} have been prepared and physico-chemically characterized. IR and electronic spectra of the complexes have been obtained. The thiosemicarbazones bind to the metal as dianionic ONS donor ligands in all the complexes except in [Ni(HL¹)₂] (1). In compound 1, the ligand is coordinated as a monoanionic (HL⁻) one. The magnetic susceptibility measurements indicate that all the complexes are mononuclear and are diamagnetic. The complexes were given the formulae [Ni(HL¹)₂] (1), [NiL¹py] (2), [NiL¹α-pic] (3), [NiL¹γ-pic] · H₂O (4), [NiL²py] (5) and [NiL²γ-pic] (6). The structures of compounds 2 and 3 have been solved by single crystal X-ray crystallography and were found to be distorted square planar in geometry with coordination of azomethine nitrogen, thiolato sulfur, phenolato oxygen and pyridyl nitrogen atoms.     

N-acetyl-DL-leucinate cobalt(II), nickel(II) and zinc(II) complexes

Summary Complexes of the type M(AcLeu)₂ · B₂ (M = Co^II, Ni^II or Zn^II; B = H₂O, py, 3-pic, 4-pic; AcLeu =N-acetyl-DL-leucinate ion) and M(AcLeu)₂ B (M = Co^II or Zn^II and B = o-phen) were prepared and investigated by means of magnetic and spectroscopic measurements. The i.r. spectra of all the complexes are consistent with bidentate coordination of the amino acid to the metal ion. The room temperature solid state electronic spectra indicate that the symmetry of this species is closer toD _4h and that MO₆ and MO₄N₂ chromophores are present in the M(AcLeu)₂ · 2 H₂O and M(AcLeu)₂B_n · x H₂O (B = py, 3-pic, 4-pic, n=2 and x=0 for M = Ni^II; B = o-phen, n=1 and x=0 for M = Co^II; B = py, 3-pic, 4-pic, n=1 and x=1 for M = Co^II) complexes, respectively. By comparing the Dq values of the amino acid and those of other N-substituted amino acids previously studied, a spectrochemical series of the the cobalt(II) and nickel(II) complexes is proposed. The¹ H n.m.r. spectra of the zinc(II) complexes confirm the proposed stereochemistry.     

Synthesis and structural characterization of manganese(III,IV) and ruthenium(III) complexes derived from 2-hydroxy-1-naphthaldehydebenzoylhydrazone

Reaction of 2-hydroxy-1-naphthaldehydebenzoylhydrazone(napbhH₂) with manganese(II) acetate tetrahydrate and manganese(III) acetate dihydrate in methanol followed by addition of methanolic KOH in molar ratio (2 : 1 : 10) results in [Mn(IV)(napbh)₂] and [Mn(III)(napbh)(OH)(H₂O)], respectively. Activated ruthenium(III) chloride reacts with napbhH₂ in methanolic medium yielding [Ru(III)(napbhH)Cl(H₂O)]Cl. Replacement of aquo ligand by heterocyclic nitrogen donor in this complex has been observed when the reaction is carried out in presence of pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF (N,N-dimethyl formamide) of these complexes suggest non-electrolytic and 1 : 1 electrolytic nature for manganese and ruthenium complexes, respectively. Magnetic moment values of manganese complexes suggest Mn(III) and Mn(IV), however, ruthenium complexes are paramagnetic with one unpaired electron suggesting Ru(III). Electronic spectral studies suggest six coordinate metal ions in these complexes. IR spectra reveal that napbhH₂ coordinates in enol-form and keto-form to manganese and ruthenium metal ions in its complexes, respectively. ESR studies of the complexes are also reported.     

Synthesis,characterization, reactivity,and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂]?·?nH₂O (where A?=?py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN?=?bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.     

Theoretical Study of the Solvent Effect on the Methyltrioxorhenium/Hydrogen Peroxide System

The effect of solvent on the stability and reactivity of methyltrioxorhenium (MTO) for activation of hydrogen peroxide (H₂O₂) was investigated theoretically. The possible geometries for all Re complexes present in this system, MTO, monoperoxo complexes [A: MeReO₂(η ²–O₂) and A·H ₂ O: MeReO₂(η ²–O₂)(H₂O)], and bisperxo complexes [B: MeReO(η ²–O₂)₂ and B·H ₂ O: MeReO(η ²–O₂)₂(H₂O)] were calculated. Based on the theoretical calculations, species A lacks coordinated water while species B·H ₂ O definitely has water coordinated to the Re. The changes of thermodynamic parameters (ΔH and ΔG) for six reactions in the MTO/H₂O₂, system including formation of mono- and bisperoxo complexes, were determined.     

Synthesis and characterization of mixed ligand complexes of cobalt(II) with some nitrogen and sulfur donors

Mixed ligand complexes of Co(II) with nitrogen and sulfur donors, Co(OPD)(S–S) · 2H₂O and Co(OPD)(S–S)L₂ [OPD = o-phenylenediamine; S–S = 1,1-dicyanoethylene-2,2-dithiolate (i-MNT^2?) or 1-cyano-1-carboethoxyethylene-2,2-dithiolate (CED^2?); L = pyridine (py), α-picoline (α-pic), β-picoline (β-pic), or γ-picoline (γ-pic)], have been isolated and characterized by analytical data, molar conductance, magnetic susceptibility, electronic, and infrared spectral studies. The molar conductance data reveal non-electrolytes in DMF. Magnetic moment values suggest low-spin and high-spin complexes. The electronic spectral studies suggest distorted octahedral stereochemistry around Co(II) in these complexes. Infrared spectral studies suggest bidentate chelating behavior of i-MNT^2?, CED^2?, or OPD while other ligands are unidentate in their complexes.     

Synthesis and structural characterization of mixed ligand complexes of nickel(II) with 1-cyano-1-carboethoxyethylene-2,2-dithiolate and some nitrogen donors

Mixed ligand complexes of Ni^II ion with 1-cyano-1-carboethoxyethylene-2,2-dithiolate (CED²⁻[S₂C = C (CN)(COOC₂H₅)]²⁻) as a primary ligand and o-phenylenediamine (OPD), pyridine (py), α-picoline (α-pic), β-picoline (β-pic) or γ-picoline (γ-pic) as secondary ligands have been isolated and characterized on the basis of analytical data, molar conductance, magnetic susceptibility, electronic and infrared spectral studies. The molar conductance data reveal that the complexes have 1:1 electrolytic nature in DMF solution. Magnetic and electronic spectral studies suggest distorted octahedral stereochemistry around Ni^II ion in its complexes. Infrared spectral studies suggest bidentate chelating behaviour of CED²⁻ ion and OPD while other ligands show unidentate behaviour in their complexes.     

Synthesis and characterization of manganese(IV) and ruthenium(III) complexes derived from bis (2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone

Bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone(naohH₄) interacts with manganese(II) acetate in methanol followed by addition of KOH giving [Mn^IV(naoh)(H₂O)₂]. Activated ruthenium(III) chloride reacts with naohH₄ in methanol yielding [Ru^III(naohH₄)Cl(H₂O)Cl₂]. The replacement of aquo by heterocyclic nitrogen donor in these complexes has been observed when the reaction is carried out in presence of heterocyclic nitrogen donors such as pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF for these complexes suggest non-electrolytic nature. Magnetic moment values suggest +4 oxidation state for manganese in its complexes, however, ruthenium(III) complexes are paramagnetic with one unpaired electron. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that naohH₄ coordinates in enol-form and keto-form to manganese and ruthenium, respectively. ESR and cyclic voltammetric studies of the complexes have also been reported.     

Spectral properties and solution behavior of gold(III) coordination compounds with water-soluble porphyrins

Gold(III) coordination compounds with three water-soluble porphyrins―5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H₂TSPP^4–), 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (H₂TMPyP⁴⁺), and 5,10,15,20-tetrakis(4-N,N,N-trimethylaminophenyl)porphyrin (H₂TTMAPP⁴⁺)―have been studied. Complex [Au(TTMAPP)]⁵⁺ has been prepared for the first time. The analysis of coordination-induced shifts of proton signals in NMR spectra and intensities of Q bands in absorption spectra indicates the high degree of bond covalence in the studied metal porphyrins and a partial transfer of electron density from porphyrin to gold ion. The cationic complexes [Au(TMPyP)]⁵⁺ and [Au(TTMAPP)]⁵⁺ in aqueous solutions has been found to exist in monomeric form, while anionic complex [Au(TSPP)]^3– undergoes dimerization upon growth of concentration and solution ionic strength. Equilibrium constant for dimerization has been calculated, the constant has been found to decrease when temperature rises. Thermodynamic parameters of dimerization process have been determined: ΔH° =–31.8 kJ/mol and ΔS° =–13.8 J/mol K.     

Theoretical Study of Substituent Effect in Aryl Group Migration in (<Emphasis Type="Italic">para</Emphasis>-C<Subscript>6</Subscript>H<Subscript>4</Subscript>X)Mn(CO)5 Complexes

In this study, we report substituent effect on aryl group migration in (para-C₆H₄X)Mn(CO)₅ complexes using mpw1pw91 quantum chemical calculations. These calculations reveal good linear relationships between barrier energy (ΔE), activation energy (ΔH^?), activation free energy (ΔG^?) values and rate constants with Hammett constants of X-substituents. The occupancy values of Mn–CO_cis and Mn–C(O)-(para-C₆H₄X) bonds in reactant, transition state and product were calculated by Natural bond orbital (NBO) method.     

Heat capacity and dual spin-transitions in the crossover system [Fe(2-pic)3]Cl2·EtOH

The heat capacity of [Fe(2-pic)₃]Cl₂·C₂H₅OH Crystal (2-pic: 2-picolylamine) has been measured with an adiabatic calorimeter between 13 and 315 K. Two phase transitions centered at 114.04 and 122.21 K were observed. This finding accords with recent prediction of possible existence of two-step spin-conversion (H. Köppen et al., Chem. Phys. Lett., 91 (1982) 348). The total transition enthalpy and entropy amounted to ΔH = 6.14 kJ mol^?1 and ΔS = 50.59 J K^?1 mol^?1. The transition entropy consists of the magnetic contribution (13.38 J K^?1 mol^?1), the orientational order-disorder phenomenon of the solvate ethanol molecule (8.97) and the change in the phonon system, in particular the change in stretching and deformation vibrations of the metal-ligand (28.24).     

Synthesis and spectral studies on heterobimetallic complexes of manganese and ruthenium derived from N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide

The complex [Mn^IV(napbh)₂] (napbhH₂ = N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide) reacts with activated ruthenium(III) chloride in methanol in 1 : 1.2 molar ratio under reflux, giving heterobimetallic complexes, [Mn^IV(napbh)₂Ru^IIICl₃(H₂O)] · [Ru^III(napbhH)Cl₂(H₂O)] reacts with Mn(OAc)₂·4H₂O in methanol in 1 : 1.2 molar ratio under reflux to give [Ru^III(napbhH)Cl₂(H₂O)Mn^II(OAc)₂]. Replacement of aquo in these heterobimetallic complexes has been observed when the reactions are carried out in the presence of pyridine (py), 3-picoline (3-pic), or 4-picoline (4-pic). The molar conductances for these complexes in DMF indicates 1 : 1 electrolytes. Magnetic moment values suggest that these heterobimetallic complexes contain Mn^IV and Ru^III or Ru^III and Mn^II in the same structural unit. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that the napbhH₂ ligand coordinates in its enol form to Mn^IV and bridges to Ru^III and in the keto form to Ru^III and bridging to Mn^II.     

Charge-transfer complexes of meso-substituted porphines

Charge-transfer (CT) complexes of 5,10,15,20-tetramethyl-21H,23H-porphine [H₂(tmp)] and 5,10,15,20-tetraphenyl-21H,23H-porphine [H₂(tpp)] have been prepared with TCNQ-type (TCNQ = 7,7,8,8-tetracyanoquinodimethane) acceptors. The complexes crystallize in a mixed-stacked structure. The electronic state of the complexes has been investigated by combining structural geometry information of the acceptors with vibrational spectroscopy data. The complexes were found to possess neutral ground states. The difference between the donor oxidation potential and the acceptor reduction potential (ΔE) also supports this designation of their electronic states. The CT absorption energy shows a linear correlation with ΔE, which is expected for CT complexes in their neutral ground states. The frontier orbitals of the porphyrin donor that participate in the CT interactions have been examined by calculating the overlap integral between the donor occupied molecular orbitals and acceptor LUMO in the complexes. In the H₂(tmp) and H₂(tpp) complexes, a_2u- and a_1u-type porphyrin HOMO and next-HOMO, respectively, are suggested to both be contributors to the establishment of π–π* CT interactions and formation of the complex.     

Heterogeneous reactions of solid nickel(II) complexes,V

The kinetics of the thermal decomposition of solid complexes of the type Ni(NCS)₂L₂ (L=pyridine,β-picoline and quinoline), of pseudooctahedral configuration, were studied by using isothermal methods, on the basis of losses of weight, in the temperature range 90–191?. The most suitable reaction order for all the complexes under investigation was found to ben=2/3, i.e. the total decomposition rate is determined by the chemical process proper. The calculated values ofE _a(in kcal · mole^?1) decrease in the following order: Ni(NCS)₂py₂ (29.4)>Ni(NCS)₂(β-pic)₂ (27.6)>Ni(NCS)₂Q₂ (24.3). With increasing volume of the ligand L the reaction rate also increases, and this suggests that the reaction proceeds by dissociative activation. For all the investigated complexes it was found that δH>E _A; this may be explained by a several-step mechanism and the complex Ni(NCS)₂L is then considered an intermediate.     

A thermodynamic study of interaction of Ag+, Mg2+, Ca2+, and K+ cations with 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine in some binary mixed non-aqueous solvents

In the present work the complexation process between Ag⁺ and Mg²⁺ cations and 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine (HBFPY) ligand was studied in pure dimethylformamide (DMF), ethanol (EtOH), acetonitrile (AN) and in (DMF-EtOH), (AN-EtOH) and (DMF-AN) binary mixed solvent solutions at different temperatures using the conductometric method. Also in this work the complexation reaction between Ca²⁺, K⁺ cations and HBFPY ligand, was studied in pure dimethylformamide (DMF), propanol (PrOH), 1,4-dioxane (DOX), ethanol (EtOH) and in DMF-PrOH, DMF-DOX and DMF-EtOH binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between this ligand and the studied cations is 1 : 1 [ML]. In most cases, addition of HBFPY to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The stability constant of [Mg(HBFPY)]²⁺ complex in various neat solvents at 15°C decreases in order: EtOH > DMF > AN and the stability constant of [Ag(HBFPY)]⁺ complex in various neat solvents at 35°C decreases in order: DMF > EtOH. The values of standard enthalpy changes (ΔH° _c ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (ΔS° _c ) were calculated from the relationship ΔH° _c,295.15= ΔH° _c –298.15ΔS° _c .     

Synthesis,crystal structures,thermal, and spectroscopic properties of four new metal(II) (M = Co,Ni, Cu,Hg) complexes of 2-benzoylbenzoate with 3-picoline

Four 2-benzoylbenzoate (bba) complexes, [Co(bba)₂(H₂O)₂(3-pic)₂] (1), [Ni(bba)₂(H₂O)₂(3-pic)₂] (2), [Cu(bba)₂(3-pic)₂] (3), and [Hg(bba)₂(3-pic)₂] (4), have been synthesized and characterized by IR spectra, thermal (TG, DTG, and DTA) analysis, and single crystal X-ray diffraction. All the complexes consist of neutral monomeric units with 1 and 2 crystallizing in the orthorhombic (P n a 2₁), 3 in triclinic (P 1), and 4 in monoclinic (P2₁/c) crystal systems. The metal(II) ions exhibit distorted octahedral coordination for 1, 2, and 3 and mercury(II) exhibits distorted trigonal prism coordination. In 1 and 2, bba is monodentate, whereas in 3 and 4 bba is bidentate. 3-Picoline (3-pic) is a classical N-monodentate ligand. Bba are coordinated to metal(II) with carboxylates and IR spectra of all complexes display characteristic absorptions of carboxylate {υ(OCO)_asym and υ(OCO)_sym}. Thermogravimetric (TG) analyses show that 1 and 2 are thermally stable (T_decomp.?>?60°C) and 3 and 4 are thermally stable (T_{decomp .} ?>?120°C).