Bis(Dimethylphosphino)ethane and related complexes of transition metals

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Niobium tetrahalide complexes with neutral diphosphine ligands

The reactions of NbCl4 with diphosphine ligands o-C6H4(PMe2)2, Me2PCH2CH2PMe2 or Et2PCH2CH2PEt2 in a 1:2 molar ratio in MeCN solution produced eight-coordinate [NbCl4(diphosphine)2]. [NbBr4(diphosphine)2] (diphosphine = o-C6H4(PMe2)2 or Me2PCH2CH2PMe2) were made similarly from NbBr4. X-ray crystal structures show that [NbCl4{o-C6H4(PMe2)2)2}] has a dodecahedral geometry but the complexes with dimethylene backboned diphosphines are distorted square antiprisms. The Nb-P and <P-Nb-P angles are very similar in the two types, but Nb-Cl distances are ~ 0.1Å longer in the square antiprismatic complexes. These paramagnetic (d1) complexes were also characterised by microanalysis, magnetic measurements, IR and UV-visible spectroscopy. Using a 1:1 molar ratio of NbCl4 : diphosphine (diphosphine = Me2PCH2CH2PMe2, Et2PCH2CH2PEt2, Cy2PCH2CH2PCy2 and Ph2PCH2CH2CH2PPh2) afforded [NbCl4(diphosphine)] and [NbBr4(Me2PCH2CH2PMe2)] was obtained similarly. These 1 : 1 complexes are unstable in solution, preventing X-ray crystallographic study, but based upon their diamagnetism, IR, UV-visible and 31P{1H} NMR spectra they are formulated as halide-bridged dimers [(diphosphine)X2Nb(μ-X)4NbX2(diphosphine)] with single Nb-Nb bonds and chelating diphosphines. The Nb(IV) complexes are prone to hydrolysis and oxidation in solution and the structures of the Nb(V) complexes [NbBr4(Me2PCH2CH2PMe2)2][NbOBr4(MeCN)] with a dodecahedral cation, and [{NbOCl3{Et2P(CH2)2PEt2}}2{μ-Et2P(CH2)2PEt2}] which contains seven-coordinate Nb(V) centres with a symmetrical diphosphine bridge are reported. The structure of niobium tetrabromide, conveniently made from NbCl4 and BBr3, is a chain polymer with edge-linked NbBr6 octahedra and alternating long and short Nb-Nb distances, the latter ascribed to Nb-Nb bonds

Phenolic and flavonoid content of Elaeagnus angustifolia L. (leaf and flower)

Objectives: Leaves and flowers ofElaeagnus angustifolia contain phenolic and flavonoid compounds. These compounds have antioxidant properties that protect cells from oxidative damage. The aim of this study was to determine and analyze total phenolic and flavonoid content of leaves and flowers in two E. angustifolia variants using different solvents (ethanol and methanol). Materials and Methods: Ethanolic and methanolic extracts of the plant leaves and flowers were prepared. Experiments were carried out to measure their phenolic and flavonoid content using two solvents. Data were analyzed using Instat-N software. Results:Results showed that the amount of phenolic and flavonoid compounds in both ethanolic and methanolic extracts was higher in Fariman variant compared with Mashhad variant. Ethanolic and methanolic extracts of Fariman variant had the highest amount of phenolic compound (10.91±0.18, 10.28± 0.36 mgGAE/100gFW, respectively) and also the highest amounts of flavonoids (5.80±0.10, 3.36±0.05 mgQE/100gFW, respectively). Phenolic and flavonoids compounds were better extracted using methanol and ethanol solvent. Conclusion: In both varieties and solvents, the amount of phenolic and flavonoids compounds in leaves were higher than flowers. In addition, the phenolic and flavonoids compounds were higher in Fariman compared to Mashhad variants