Binuclear ruthenium(II) pyridazine complex catalyzed transfer hydrogenation of ketones

A convenient and general method of synthesis of binuclear ruthenium(II) pyridazine complex was reported. The synthesized complex was characterized by analytical and spectral methods. The structure of the complex was confirmed by X-ray diffraction technique and was found to be an efficient catalyst for the transfer hydrogenation of ketones with excellent conversions in the presence of isopropanol/KOH at 82 °C. The effect of solvents, bases, and different catalyst/substrate ratio for the reaction was also investigated.     

The Determination of the Titre of Ascorbic Acid Standard Solutions

Abstract

A new method for the determination of the titre of ascorbic acid standard solutions employing potassium dichromate as a primary standard has been developed. In a pyrophosphate medium, the pyrophosphate complex of divalent manganese is oxidized by dichromate to the pyrophosphate complex of tervalent manganese; the latter oxidizes o-tolidine reversibly with formation of the corresponding quinonediimine, which is visually titrated by the ascorbic acid standard solution.     

Synthesis and Structure of Bis(2-Amino-5-Cyanopyridinium) Diaquadichlorocopper(II) Dichloride

The reaction of CuCl₂ with 2-amino-5-cyanopyridine and HCl in 1-propanol gave bis(2-amino-5-cyanopyridinium) diaquadichlorocopper(II) dichloride (1). Crystal data for 1 are: monoclinic, space group: P2₁/c, a = 8.461(3) Å, b=14.665(5) Å, c=7.883(3) Å, g =96.105(4)°, V=972.6(6) Å 3 , Z=2, D_calc =1.645 Mg/m³, w =1.691 mm^?1, F(OOO)=486, MoK _f( u =0.71073 Å), R1=0.0431 for [∣I∣ S 2 σ (I)] and R1=0.0680 for all 1944 unique reflections and 130 parameters. The structure exists as square planar Cu(H₂O)₂Cl₂ units with long semi-coordinate bonds to the cyano nitrogens of the 2-amino-5-cyanopyridinium ions. Hydrogen bonding from the water molecules and N―H hydrogens to the chloride irons stablises the lattice.     

An unprecedented tetranuclear Zn(ΙΙ) complex with an unsymmetric Salen-type bisoxime ligand: synthesis,crystal structure,and spectral properties

A tetranuclear Zn(ΙΙ) complex, [Zn₄L₂(OAc)₂(CH₃OH)₂] with an unsymmetric Salen-type bisoxime (H₃L?=?6-hydroxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol), has been synthesized and structurally characterized. There are two kinds of coordination geometry (trigonal bipyramidal and square pyramidal) in the Zn(ΙΙ) complex. The molecule has serious distortion probably from the asymmetry. The complex exhibits blue emission with the maximum emission wavelength λ _max?=?423?nm when excited with 340?nm.     

Synthesis,structure, and luminescence of rhenium(I) complexes with substituted bipyridines

Two new rhenium(I) complexes chelated by a substituted 2,2′-bipyridine with general formula Re(CO)₃LCl, where L?=?6?-(2″-methoxyphenyl)-2,2′-bipyridine (L₁ ) and 6?-(4″-diphenylaminophenyl)-2,2′-bipyridine (L₂ ), are synthesized and characterized by IR, NMR, and elemental analysis. Structure of 1 was determined by single-crystal X-ray crystallography, revealing that rhenium is six-coordinate octahedral. The electrochemical, photophysical, and thermal properties of the two rhenium(I) complexes were investigated. Electroluminescent devices were fabricated by doping 1 in polymer blend host of poly(vinylcarbazole) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole using simple solution spin-coating technique. The device exhibits a maximum current efficiency of 2.97?cd?A^?1 and peak brightness in excess of 2390?cd?m^?2.     

Bis-chelate Fe(III) complex of an azomethine at the focal point of a branched ester functionalized with cyclohexylbenzoic acid

A Fe(III) complex with Cl counter ion based on a branched Schiff base has been synthesized and studied. The compound was produced by the reaction of the Schiff base with FeCl₃ at room temperature in benzene–ethanol. The complex is symmetric, i.e., bis-chelate, with an octahedral coordination of Fe. The compound revealed phase transitions of the “solid–solid” type. The complex displayed a temperature-induced spin transition (S?=?1/2???5/2) which was detected by EPR.     

Two diamond-type octacyanometallate(IV)–nickel(II) assemblies chelated by macrocyclic ligands

Two octacyanometallate-based Ni^II–M^IV [M?=?Mo(1), W(2)] bimetallic assemblies chelated with tetradentate macrocyclic ligands have been synthesized by slow diffusion and characterized structurally. In both complexes, M and Ni centers acting as linker and connector, respectively, are connected by M–CN–Ni–NC–M linkages to form a 3-D diamond-type topological network. Magnetic behaviors of both complexes show a very weak antiferromagnetic interaction between Ni^II ions mediated by the diamagnetic [M(CN)₈]^4? bridges.     

Two photoluminescent pentanuclear homo- and hetero-metal complexes based on benzotriazole bridge

Two new discrete Btz-bridged pentanuclear metal complexes, [HDMF][NaHg₄(Btz)₆I₄] (1) and [Zn₅(Btz)₆(L)₃(Ac)]?·?0.5MeOH?·?0.5H₂O (2) (Btz?=?deprotonated benzotriazole, L?=?p-aminobenzoate, HDMF?=?protonated DMF, and Ac?=?acetate), were synthesized using three-layered diffusion and natural evaporation methods, respectively. In 1, the pentanuclear anion [NaHg₄(Btz)₆I₄]^? is composed of a tetrahedral arrangement of four four-coordinate Hg(II) ions centered on the six-coordinate Na(I), and thereby forming a rare Btz-bridged hetero-metal complex. Compound 2 is a neutral pentanuclear homo-metal complex, consisting of a tetrahedral arrangement of four five-coordinate Zn(II) ions centered on the fifth six-coordinate Zn(II). The thermal stabilities and solid-state photoluminescence of the two complexes have been investigated.     

Synthesis and crystal structure of bis(m-hydroxybenzoato(1-))bis(benzimidazole) copper(II) dihydrate

The crystal structure of the title complex was determined by single-crystal X-ray diffraction methods. The unit cell contains two independent molecules, A and B. B is a mononuclear Cu(II) complex with square-planar coordination geometry formed by two benzimidazole molecules and two hydroxylbenzoate anions. A is a dimer of B, formed by bridging hydroxybenzoate, and copper assumes square-pyramidal geometry. Aromatic π–π stacking is observed between parallel benzimidazole rings of neighboring A molecules. IR spectra of the compound are assigned in line with the crystal structure.     

High-spin iron(III) complexes: structural,spectroscopic, and photochemical studies

Reaction of FeCl₃ with one equivalent of acac (acac = pentane-2,4-dionate) and KTp^Me2 (Tp^Me2 = hydrotris(3,5-dimethyl-pyrazol-1-yl)borate) yielded Tp^Me2Fe(acac)Cl (3), which upon reaction with methanolic solution of sodium azide resulted in the formation of a six coordinate compound Tp^Me2Fe(acac)N₃ (4) with a single azide. When the reaction of FeCl₃ and KTp^Me2 was performed with two equivalents of sodium azide and one equivalent of 3,5-dimethylpyrazole (Pz^Me2H), a six coordinate cis azide compound [Tp^Me2Fe(Pz^Me2H)(N₃)₂] (5) was obtained. These compounds were characterized by spectroscopic methods and single crystal X-ray crystallography. Electrochemical studies of 5 show that it can be irreversibly reduced at relatively lower potential than 4. The photolysis of 5 was performed at 77 K at different wavelengths (480, 419, and 330 nm) showing that 5 was photoreduced to a high-spin Fe(II) species instead of photooxidized to Fe(V).