Synthesis and Characterization of Bimetallic Nickel and Cobalt Carbonyl Complexes Containing Stannyl Groups

The bimetallic NiSn₂ complex Ni(SnBu₃^t)₂(CO)_3, 1, was obtained from the reaction of Ni(COD)₂ and Bu₃^tSnH and CO. The reaction of Co₂(CO)₈ and Bu₃^tSnH afforded the bimetallic Co–Sn complex Co(SnBu₃^t)(CO)₄, 3. Compound 3 was also obtained from the reaction of Co₄(CO)₁₂ and Bu₃^tSnH but in a lower yield. Both compounds 1 and 3 were characterized by single crystal X-ray diffraction, and possess trigonal bipyramidal geometries around the transition metal centre with two and one stannyl ligands, respectively.     

Elastic properties and spectroscopic studies of lithium lead borate glasses

Elastic properties of xLi₂O — 20PbO — (80-x)B₂O₃ glasses have been measured at a frequency of 10 MHz using X-cut and Y-cut quartz transducers. The trends in the variation of elastic moduli, Poisson’s ratio and Debye temperature have been studied. The elastic moduli namely longitudinal and young’s modulus show strong linear dependence while bulk and shear modulus vary marginally as a function of Li₂O concentration. The Poisson’s ratio is found to be almost constant and Debye temperature increases with the increase of Li₂O concentration. IR, MAS-NMR and glass transition temperature studies have been also carried out. Glass transition temperature is found to increase with increase of Li₂O concentration. IR and MAS-NMR spectra show characteristic features of borate network and systematic change as a function of Li₂O concentration. The variation in the elastic properties and structural features of IR and MAS-NMR indicate that Pb²⁺ ions are likely to occupy network forming positions in this glass system. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

4-Anilinopyrimido[4',5':4,5]selenolo(2,3-b)quinoline and 4-piperazino pyrimido[4',5':4,5]selenolo(2,3-b)quinoline: new DNA intercalating chromophores with antiproliferative activity

We have used circular dichroism, hydrodynamic methods, absorbance, and fluorescence titration to study the interaction of 4-anilinopyrimido[4',5':4,5] selenolo (2,3-b)quinoline (APSQ) and 4-piperazinopyrimido[4',5':4,5] selenolo(2,3-b)quinoline (PPSQ) with DNA. The association constants of APSQ and PPSQ were of the order of 10(4)M(-1). The fluorescence properties at ionic strength 0.01M are best fit by the neighbor exclusion model, with K=0.58-9.2 x 10(4)M(-1) and an exclusion parameter of 0.9-6.4 bp. Binding to the GC-rich DNA of Micrococcus lysodeikticus was stronger than the binding to calf thymus DNA, suggest that drug binds preferentially to G+C pairs at low r. CD spectra indicate that stacking of these compounds with DNA induces a strong helicity in the usually disordered structure of this double strand. Viscosity experiments show with sonicated calf thymus DNA with PPSQ an twice increase in slope (m) as that with APSQ. PPSQ increases the T(m) for calf thymus DNA melting by approximately 10 degrees C as binding approaches saturation, with biphasic melting. The cytotoxicities of these compounds on leukemia HL-60, K-562, B16F10 melanoma and Colo-205 are quite similar and inhibition (IC(50)) was in the range of 0.39-9.80 microM. The anticancer efficacy against B16F10 melanoma has provided evidence of major anticancer activity for PPSQ. Single or multiple intraperitonial (i.p.) doses of drug proved high level activity against the subcutaneous (s.c.) grafted B16 melanoma, significantly increase in life span (ILS 139% and 170%). The aim of this study was to analyze the physiochemical properties of these compounds in an attempt to understand its superior biological activity.     

Radical Exchanges and Structural Transformations on the Iron Carbonyl-Bulky Tin Cluster Complex, Fe2(μ-SnBu 2 t )2(CO)8 by Solvents Toluene, Xylenes and Ethylbenzene

The reaction of Fe₂(CO)₉ and Bu ₃ ^t SnH yielded the bimetallic cluster complexes Fe₂(??-SnBu ₂ ^t )₂(CO)₈, 1, and Fe₄(??₄-Sn)(??-SnBu ₂ ^t )₂(CO)₁₆, 3. Compound 3 contains two Fe₂(CO)₈(??-SnBu ₂ ^t ) groups held together by a central quadruply bridging tin atom, giving an overall bow-tie structure for the one tin and four iron atoms. Refluxing compound 1 in toluene solvent affords the complex Fe₂[??-SnBu^t(CH₂Ph)]₂(CO)₈, 4, where two of the Bu^t groups in 1 have been replaced with benzyl groups, as a result of selective benzylic C?CH bond activation of solvent toluene. Similarly refluxing compound 1 in ortho-, meta- and para-xylene solvents gives the complexes where two, three and four of the Bu^t groups in 1 have been replaced by the respective xylyl groups. Compound 1 also reacts with ethylbenzene to furnish the complex Fe₂[??-SnBu^t(MeCHPh)]₂(CO)₈, 14, where two of the Bu^t groups in 1 have been replaced as a result of the benzylic C?CH activation of ethylbenzene. A mechanism based on a radical pathway is proposed for the selective C?CH bond activation by 1.     

Hydrophilic Pd-phosphines catalyzed one-pot synthesis of substituted isoquinolines,furopyridines and thienopyridines in aqueous medium

A first example of simple and efficient hydrophilic Pd-phosphine complexes catalyzed one-pot three-component reaction of ortho-bromo aldehydes, terminal alkynes and ammonium acetate proceeds through the tandem coupling-imination-annulation path for the synthesis of substituted isoquinolines, furopyridines and thienopyridines in good to excellent yields in green aqueous medium at mild temperature was described.     

Novel Quinolone Derivatives: Synthesis and Antioxidant Activity

Russian Journal of General Chemistry - Novel quinolone derivatives have been designed and readily synthesized according to a simple protocol including O-alkylation and Claisen rearrangement...     

AgI-promoted one-pot synthesis of aminoindolizines via sequential Mannich-Grignard addition and intramolecular cyclization in water

The efficient synthesis of aminoindolizines in ecofriendly water with broad substrate scope from the mild and readily available AgI-catalyzed one-pot three-component reaction of pyridine-2-carboxaldehyde, secondary amines, and terminal alkynes proceeds through the sequential Mannich-Grignard addition as well as intramolecular cyclization was reported for the first time.     

A Bimetallic Iron–Nickel Cluster from the Reaction of Nickelocene with a Pentairon Carbonyl Carbide Cluster Complex

The new bimetallic Fe–Ni carbide containing cluster complex, Fe₄Ni(Cp)₂(CO)₁₀(μ₅-C), 4 was afforded by metal–metal exchange and metal cluster rearrangement processes in the reaction of Fe₅(μ₅-C)(CO)₁₅, 1, with NiCp₂ at 80 °C. A minor product Fe₅(Cp)₂(CO)₁₀(μ₅-C), 5, was also obtained from this reaction which contains no nickel and is a di-Cp substituted derivative of 1. Both compounds were characterized by a combination of IR, ¹H NMR, mass spectrometry, elemental and single crystal X-ray diffraction analyses. Compound 4 consists of an open Fe₄Ni(μ₅-C) cluster framework with a carbide ligand where one iron atom bridges a butterfly arrangement of one nickel and three iron atoms.     

Avoiding convergence problems in VLE predictions using an equation of state

Owing to certain advantages, the equation-of-state (EOS) approach is preferable to mixed models for VLE predictions in hydrocarbon processing at high pressures. However, the EOS approach leads to convergence problems, typically yielding what are referred to as trivial solutions for single models. Despite the use of this approach for over three decades, not much attention has been given to this aspect until recently. An attempt is made here to analyse the problem systematically and to suggest a solution. A procedure, providing initial estimates of pressure and temperature for VLE predictions, is also a long-felt need. Correlations are suggested for this purpose. Finally, an algorithm is proposed which can resolve trivial solutions and other convergence problems.