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Two tetranuclear and two mononuclear Cu(II) complexes with arylhydrazones of malononitrile derived ligands (compounds 1–2 and 3–4, respectively), one trinuclear Co(II/III) complex with an arylhydrazone of acetoacetanilide (5) and one tetranuclear Zn(II) complex of 3-(2-carboxyphenyl-hydrazone)pentane-2,4-dione (6) were screened as potential catalysts in the peroxidative oxidation of cyclohexane by aqueous H2O2 in acetonitrile. The best results were attained in the presence of pyrazine-2-carboxylic acid (PCA) with 1 (26% yield, TON = 52.0) and with 2 (24%, TON = 48.0) after 4 h at 40 °C. In the presence of complexes 5 and 6, no oxygenated products were detected in the studied conditions. The employment of non-conventional conditions like supercritical carbon dioxide (scCO2) as reaction medium or microwave (MW) irradiation was assessed for complexes 1 and 2. After 6 h in acetonitrile–scCO2, at 50 °C and with HNO3 as promoter, only 17% yield was achieved using 1 as catalyst, and 21% using 2. Total yields of oxygenates up to 14 (with 1) and 13% (2) and TOFs of 56.0 and 52.0 h−1, respectively, were obtained working under MW irradiation at 70 °C and for the much shorter time of 0.5 h. [ABSTRACT FROM AUTHOR]

The tridentate, monoanionic bis(oxazolinylmethylidene)‐isoindolate pincer ligand was utilized for the synthesis of various cobalt(II) high‐spin complexes. Employing standard complexation procedures, the corresponding acetato and chlorido complexes were isolated in good yields and thoroughly characterized in the solid‐state and in solution. In particular, a density functional theory (DFT) supported paramagnetic NMR analysis revealed a strong correlation between observed 13C NMR shifts and calculated spin‐density distributions, allowing for an unambiguous signal assignment in all 1H and 13C NMR spectra. An acetato‐bridged trinuclear cobalt species as well as the hexacoordinate "homoleptic" complex [(Rboxmi)2Co] were further identified as side products generated in the complex synthesis. The chlorido complexes were applied as catalysts for the cobalt‐catalyzed hydrosilylation of acetophenone, producing the chiral secondary alcohol with moderate enantioselectivities. [ABSTRACT FROM AUTHOR]

The new 3d metal complexes of pyrimidine-2-carboxylic (2PCA) and pyrimidine-5-carboxylic (5PCA) acids were synthesized and characterized using thermal analysis (TG–DSC, TG–FTIR), X-ray, spectroscopic (IR, Raman) methods and theoretical (DFT) studies. In the complexes of pyrimidine-2-carboxylic acid of the general formula M(2PCA)2·xH2O (where 2PCA-pyrimidine-2-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 0 for Mn and Cu; x = 2 for Co, Ni and Zn) coordination of metal ions occurs through nitrogen atom from pyrimidine ring and carboxylate oxygen atom. The complexes of pyrimidine-5-carboxylic acid of the general formula M(5PCA)2·xH2O (where 5PCA—pyrimidine-5-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 6 for Cu and 4 for remaining complexes) were obtained as monomeric isostructural compounds. Coordination of metal centers occurs through two nitrogen atom from different pyrimidine-5-carboxylate ligand and four oxygen atoms from water molecules. The IR and Raman spectra of free acids as well as obtained metal(II) complexes were described in detail. Aromaticity (HOMA, EN, GEO and I6) of complexes was determined and discussed. The investigated compounds decompose in air in two main stages connected with dehydration and decomposition/burning of anhydrous compounds to the suitable metal oxides. Thermal decomposition in nitrogen leads to the evolution of water, carbon oxides, ammonia and pyrimidine molecules. [ABSTRACT FROM AUTHOR]

The crystal structure of tetra(μ-acetato)-bis{[1-ethyl-3-(pyridine-2-yl)carbamide]copper} Cu 2(L) 2(CH 3COO) 4 ( I), where L is 1-ethyl-3-(pyridine-2-yl)carbamide, is determined. The asymmetric unit cell of the crystal structure of I contains a copper complex with two acetate ions and a monodentate molecule of 1-ethyl-3-(pyridine-2-yl)carbamide, which is coordinated via the pyridine nitrogen atom. Due to the symmetry center, binuclear complexes form in the crystal, in which the acetate ions act as bridges between the metal atoms. In them, the coordination polyhedron of the central copper atoms represents an almost ideal tetragonal pyramid. Its base is formed from the oxygen atoms of acetate ions. In the crystal of the binuclear complex, hydrogen bonds form between the acetate ions and the L ligand along with an intramolecular hydrogen bond, which stabilize the conformation of the organic L molecule. Between the neighboring complexes in the crystal, the van der Waals interaction occurs. [ABSTRACT FROM AUTHOR]

reaction of acetylacetone with the framework sandwich-type metallosiloxanes (MOS) of general formula [PhSiO]M[PhSiO], where M = Cu, Ni, Mn, was studied by GPC, H and Si NMR spectroscopy, X-ray diffraction, elemental and functional analysis. The reaction involved replacement of the metal atoms with the hydrogen atoms and is accompanied by the formation of the corresponding chelate complexes M(acac). Displacement of the metal from the framework MOS leads to the destruction of molecular skeleton and formation of phenylsiloxanes containing Si-OH groups. The yield and composition of the reaction products considerably depend on the nature of the metal in [PhSiO]M[ThSiO]. A selective substitution of the metal leads to the stereoregular hexahydroxyhexaphenylcyclohexasiloxane, [PhSiO(PH)], cis-isomer. The structure and composition of the crystalline hexahydroxyhexaphenylcyclohexasiloxane obtained were confirmed by Si NMR spectroscopy, X-ray diffraction study, and functional analysis, while its TMS derivative was studied with H NMR spectroscopy and GPC. Using a framework manganese phenylsiloxane as an example, a reversible character of the process has been established and an alternative synthesis of this compound from hexahydroxyhexaphenylcyclohexasiloxane and Mn(acac) has been accomplished for the first time. [ABSTRACT FROM AUTHOR]

Hydrazones derived from substituted benzoyl hydrazides and benzil a-monoxime [viz. benzil a-monoxime benzoylhydrazone (BMBH), benzil a-monoxime 4-chlorobenzoylhydrazone (BMPCBH), benzil a-monoxime 4-methoxybenzoylhydrazone (BMMBH), benzil a-monoxime 4-nitrobenzoylhydrazone (BMNBH) and benzil a-monoxime 2-chlorobenzoylhydrazone (BMOCBH)] have been synthesized and used in preparing the corresponding Cr(III), Mn(III), Fe(III) and Co(III) complexes. The ligands undergo deprotonation in ethanolic alkaline solution to form dinuclear complexes. The complexes are insoluble in common organic solvents, decompose above 300°C, and are spin-free octahedral. The complexes isolated were characterized by elemental analyses, IR, electronic, 1 H NMR spectra, conductance, thermal studies and magnetic susceptibility measurements. The bonding and probable structures of the complexes are discussed on the basis of the spectral and magnetic data. The ligands, as well as their complexes, show antifungal activity. [ABSTRACT FROM AUTHOR]

A novel mesogenic Schiff base, N-(4-butylphenyl) salicylaldimine (Hbpsal), was prepared and its ligational behavior towards some 3 d metal ions studied. All the metal complexes synthesized were of the general formula, [M(bpsal) 2 (H 2 O) 2 ] where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). The complexes were structurally characterized by elemental analyses, molar conductance, IR, NMR, and electronic spectral data. The metallo mesogenic phases of the Cu(II) complex were studied by optical microscope. The spectral data show that Hbpsal acts as a bidentate ligand towards the metal ions. Mesogenic studies indicate that the ligand shows a focalconic structure with smectic-A phase while the Cu(II) complex displays smectic-A as well as smectic-E phases. [ABSTRACT FROM AUTHOR]

The complexes[M(L)(H2O)x]n[M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II)] and[M2(L)3]n[M = Mn(III), Fe(III)] and[VO(HL)2] with N-picolinoyl-N′-2-furanthiocarbohydrazide(H2L) have been prepared and characterized by elemental analyses, magnetic susceptibility measurement, electronic, NMR(1H and 13C), IR and FAB mass spectral data. Physico-chemical studies indicate that the complexes are polymeric in nature. The room temperature ESR spectra of[VO(HL)2] and[Cu(L)]n complexes yield〈g〉 values, characteristic of square-pyramidal and square-planar complexes, respectively. The Mössbauer spectra of[Fe2(L)3]n at room temperature and at 78 K suggest the presence of high-spin(S = 5/2) and low-spin(S = 1/2) forms of Fe(III) in the same complex at both temperatures. The complexes of OV(IV), Fe(III), Ni(II), and Cd(II) show semiconducting behaviour in the solid state in the temperature range 307–397 K, with a band gap of 0.18–0.44 eV. The other complexes are insulators. [ABSTRACT FROM AUTHOR]

Dacarbazine (DAC) 5-(3,3-dimethyl-1-triazenyl)imidazole-4-carboxamide is an imidazole-carboxamide derivative that is structurally related to purines. DAC belongs to the triazene compounds, which are a group of alkylating agents with antitumor and mutagenic properties. DAC is a non-cell cycle specific drug, active in all phases of the cellular cycle. In the frame of this work the 3d metal complexes (cobalt and copper) with dacarbazine were synthesized. Their spectroscopic properties by the use of FT-IR, FT-Raman, and 1HNMR were studied. The structures of dacarbazine and its complexes with copper(II) and cobalt(II) were calculated using DFT methods. The effect of metals on the electronic charge distribution of dacarbazine was discussed on the basis of calculated NBO atomic charges. The reactivity of metal complexes in relation to ligand alone was estimated on the basis of calculated energy of HOMO and LUMO orbitals. The aromaticity of the imidazole ring in dacarbazine and the complexes were compared (on the basis of calculated geometric indices of aromaticity). Thermal stability of the investigated 3d-metal complexes with dacarbazine and the products of their thermal decomposition were analyzed. [ABSTRACT FROM AUTHOR]