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Two Ni(II) complexes, [Ni(dmoTSCH)Cl] (1) and [Ni(dmoPhTSCH)Cl] (2) of the tridentate thiosemicarbazone ligands diacetylmonooxime thiosemicarbazone (dmoTSCH2) and diacetylmonooxime (4-phenyl)thiosemicarbazone (dmoPhTSCH2) have been synthesized. X-ray crystal structure of [Ni(dmoTSCPhTSCH)Cl] (2) indicates that the Ni(II) assumes a square planar geometry in the complexes, with the ligand coordinated in a monoanionic N,N,S donor mode and the fourth coordination position of Ni(II) is occupied by a chloride ion. Cyclic and differential pulse voltammetric experiments suggest that the Ni(II) complexes can undergo a two electron reduction at about −1.0V. It is shown that the Ni(II) complexes in DMF or DMSO solutions can mimic CO-dehydrogenase activity by oxidizing CO to CO2in presence of a base like NaOAc and a sacrificial electron acceptor like methyl viologen and the colour of the resultant MV.+can be used to monitor the reaction.

Crystal structure and spectroscopic properties of 4-acetaminopyridine and its protonated form4-Acetaminopyridine dihydrate and its protonated form, stabilized as the hydrochloride salt have been synthesized and spectroscopic elucidated in solution and in the solid-state by means of the inear-polarized solid state IR-spectroscopy (IR-LD), UV-spectroscopy, TGA, DSC, and the positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and the electronic spectra. The spectroscopic and theoretical data are compared with the structure of the first compound obtained by single crystal X-ray diffraction. The effect of Npyprotonation on the optical and magnetic properties of a 4-acetaminopyridine is discussed.

Two new terephthalato-bridged tetranuclear polymeric NiII complexes, namely [Ni4L41(μ-tp-κ4-O)(H2O)2(μ-tp-κ2-O)]·2C2H5OH·CH3OH·3H2O (1) and [Ni4L42(μ-tp-κ4-O)(H2O)2(μ-tp-κ2-O)]·3H2O (2) [L1 = N-(3-aminopropyl)-5-bromosalicylaldimine and L2 = N-(3-aminopropyl)salicylaldimine], are reported along with the syntheses and structures of the dicyanoargentate-bridged polymeric complexes [Ni(L1)(H2O){Ag(CN)2}]α (3) and [Ni(L3)(MeOH){Ag(CN)2}]α (4) [L3 = N-(3-amino-2,2-dimethylpropyl)-5-bromosalicylaldimine]. All four complexes are found to be effective heterogeneous catalysts for the epoxidation of alkenes such as styrene, α-methylstyrene and cyclohexene in the presence of tert-butyl hydroperoxide. The variable-temperature magnetic susceptibility measurements (300–2 K) of complex 1 show a fair degree of antiferromagnetic coupling between the NiII centers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Abstract: Valinamide ester amide of squaric acid has been synthesized and structurally characterized by single crystal X-ray diffraction. Individual molecules are linked into zig-zag helix chains running parallel to [0 1 0] by N–H ⋯ O hydrogen bonds of length 2.7908(19) Å and 2.980(2) Å involving the valinamide nitrogen atoms and the amide carbonyl oxygen atom. An experimental IR spectroscopic characterization and theoretical vibrational analysis have also been performed, using the possibilities of polarized linear-dichroic IR-spectroscopy (IR-LD), based on an orientation technique of the molecules as a suspension in a nematic liquid crystal.

A new Cu(II)-complex of 3-aminopyridine, [CuCl(3-AP)4][Cu(3-AP)4(H2O)]Cl3· 2H2O (1), containing two contrasting complex cations has been synthesized and structurally characterized by single crystal X-ray diffraction and solid-state linear-dichroic infrared (IR-LD) spectral analysis. In both cations four 3-AP molecules coordinate the Cu(II) atom in a monodentate fashion through their endocyclic (Npy) nitrogens, thereby generating a square-planar coordination geometry for the CuN4chromophor. Perpendicular to the N4plane, the metal ion is coordinated by a chloride anion in the first cation and a water ligand in the second cation. One of three additional water molecules of crystallization occupies the vacant octahedral site of the second cation and participates in a weak Cu···OH2interaction. An IR-LD spectral analysis of the samples, oriented as a suspension in a nematic liquid crystal confirmed the crystallographic data and the retention of the pyridine ring aromatic character after coordination. The presented results are additionally supported by UV, 1H-NMR, EPR and MS analysis and by thermogravimetric and calorimetric data.A new Cu(II)-complex of 3-aminopyridine, [CuCl(3-AP)4][Cu(3-AP)4(H2O)]Cl3· 2H2O (1), containing two contrasting complex cations has been synthesized and structurally characterized by single crystal X-ray diffraction and solid-state linear-dichroic infrared (IR-LD) spectral analysis. In both cations four 3-AP molecules coordinate the Cu(II) atom in a monodentate fashion through their endocyclic (Npy) nitrogens, thereby generating a square-planar coordination geometry for the CuN4chromophor. Perpendicular to the N4plane, the metal ion is coordinated by a chloride anion in the first cation and a water ligand in the second cation. One of three additional water molecules of crystallization occupies the vacant octahedral site of the second cation and participates in a weak Cu···OH2interaction. An IR-LD spectral analysis of the samples, oriented as a suspension in a nematic liquid crystal confirmed the crystallographic data and the retention of the pyridine ring aromatic character after coordination. The presented results are additionally supported by UV, 1H-NMR, EPR and MS analysis and by thermogravimetric and calorimetric data.

The salicylhydrazone of anthranilhydrazide (H₂L) reacted with MoO₂(acac)₂ in refluxing alcohols to yield compounds of the general formula MoO₂L(ROH) (where R = CH₃, C₂H₅, n-C₃H₇, n-C₄H₉). The complex MoO₂L(C₂H₅OH) is found to undergo facile reaction with heterocyclic bases to form MoO₂L(Q)-type complexes where Q = pyridine, 4-picoline, imidazole and substituted imidazoles. Single crystal X-ray structural studies on the ligand H₂L (1) and the complexes MoO₂L(C₂H₅OH) (2) and MoO₂L(Imz) (3) indicate that the free ligand exists in its keto form, but in the two complexes 2 and 3 the ligand coordinates to the MoO₂2+ core through the enolate oxygen, the phenolate oxygen and the azomethine nitrogen. Reaction of MoO₂L(C₂H₅OH) with PPh₃ in CH₃CN under dry dinitrogen, in the absence and presence of bipy, produced MoIVOL (2a) (brown) and MoIVOL(bipy) (2b) (green) respectively along with Ph₃PO. This reaction is reminiscent of the oxotransfer reaction from the MoO₂+2 core of a molybdoenzyme to the substrate PPh₃. Complexes 2 and 3 crystallized in the P2₁/n and P2₁/c space groups respectively and for both of them Z = 4. The structures clearly show that 2 and 3 have distorted octahedral coordination environments in which the Mo–O(ethanol) bond of 2 and the Mo–N (imidazole) bond of 3 are significantly longer than is usually observed. This is indicative of the weak bonding of ethanol and imidazole to the MoO₂2+ core and points to the inherent weakness of the sixth coordination position of the coordination polyhedron of the MoO₂2+ core in MoO₂L(C₂H₅OH) and MoO₂L(Imz).

The cover picture shows how a novel tetranuclear NiII complex [Ni4L41(μ-tp-κ4-O)(H2O)2(μ-tp-κ2-O)]·2C2H5OH·CH3OH·3H2O [L1 = N-(3-aminopropyl)-5-bromosalicylaldimine] acts as an active catalyst for the partial oxidation of cyclohexene into its epoxide product when it is immobilized over a network of hexagonal mesoporous silica. Herein the catalytic sites allow the formation of epoxide over their surfaces. tert-Butyl hydroperoxide acts as an oxidant for the partial oxidation process. A dinuclear unit is formed, in which the NiII is bridged by a phenolato group, and two such units are connected through a terephthalate moiety to form a tetranuclear nickel(II) complex. The tetranuclear units are connected to each other by another terephthalate moiety in its bis(monodentate) mode to form one-dimensional networks. Details are described in the article by P. Banerjee et al. on p. 5033 ff. The artwork was designed by Mr. Jishnunil Chakraborty and Mr. Gopal Das.