Search results for "Chela"
showing 10 items of 415 documents
Complex Formation of the Uranyl (UO22+) Ion with the Diethylene Triaminopentaacetate (DTPA) Ligand at 25 °C in 3 M Sodium Perchlorate
2011
The complex formation between the uranyl (UO22+) ion and the diethylene triaminopentaacetate ligand (DTPA) has been investigated at 25 °C, in a 3 M sodium perchlorate medium. The overall protonation constants βjH of the free ligand have been previously determined in this ionic medium: six protonated species (HjA), with j ranging from 1 to 6, together with the free anion A5− have been identified in the concentration range from (3·10−3 to 13·10−3) mol·kg−1. Four complex species, H2UO2A−, HUO2A2−, UO2A3−, and UO2AOH4−, have been identified in the total uranyl concentration range from (1.1·10−3 to 5.7·10−3) mol·kg−1, and their overall stability constants determined, keeping the metal to ligand …
Hydrolytically active tetranuclear [NiII2]2 complexes: synthesis, structure, spectroscopy and phosphoester hydrolysis
2015
Three tetranuclear nickel(II) complexes, [Ni4(H2chdp)2(H2O)4]Br2·4CH3OH·3H2O (1), [Ni4(H2chdp)2(H2O)4](PF6)2 (2) and [Ni4(H2chdp)2(H2O)4](ClO4)2·3.2CH3OH·0.8H2O (3) have been synthesized by exploiting the flexibility, chelating ability and bridging potential of a new symmetrical μ-bis(tetradentate) ligand, H5chdp (H5chdp = N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[2-hydroxyethyl]-1,3-diaminopropan-2-ol). Complexes 1, 2 and 3 have been synthesized by carrying out reaction of the ligand H5chdp with stoichiometric amounts of NiCl2·6H2O/NaBr, NiCl2·6H2O/NH4PF6, and Ni(ClO4)2·6H2O, respectively, in methanol–water in the presence of NaOH at ambient temperature. Characterizations of the complexes ha…
Adducts of 1,4-diazabutadienes with group IIB metal halides
1981
Abstract The reactions of 1,4-diazabutadienes (or α-diimines) RNC(R′)C(R″)NR, DAB, (R = p -C 6 H 4 OMe, R′ = R″ = H, DAB I ; R = p -C 6 H 4 OMe,R′ = H, R″ = Me, DAB II ; R = p -C 6 H 4 OMe, R′= R″ = Me; DAB III ; R = CMe 3 , R′ = R″ = H, DAB IV ) with MX 2 M = Zn, Cd, Hg; X = CI, Br) yield in general 1/1 adducts. These species are assigned a monomeric configuration with a σ,σ′-N,N′, chelating DAB ligand for M = Zn, Hg, whereas the CdCl 2 adducts have polymeric structures with terminal and/or bridging chlorides. In the reactions of CdCl 2 with DAB I or DAB IV polymeric species [(CdCl 2 ) 2 (DAB)] x are obtained in which all chlorides are bridging. Spectrophotometric dissociation equilib…
Anion encapsulation promoted by anion⋯π interactions in rationally designed hexanuclear antiferromagnetic wheels: synthesis, structure and magnetic p…
2009
The reaction of Kpymca (pymca = pyrimidine-2-carboxylato anion) with MX2·6H2O and tmda (N,N,N′,N′-tetramethylethylenediamine) in 1 : 3 : 3 molar ratio, using a MeOH/water mixture (3 : 1) as solvent, afforded the hexanuclear complexes [M6(µ-pymca)6(tmda)6]X6·4H2O (M = NiII, X = ClO4−1, BF4−2; M = CoII, X = ClO4−3). The reaction of pymca with either Cu(ClO4)2·6H2O or Cu(BF4)2·6H2O did not lead to any definite product. However, in the presence of strong coordinating chloride anions the linear tetranuclear complex [Cu4(µ-pymca)3Cl(H2O)](ClO4)4·4.5H2O 4 could be obtained. The structures of 1–3 are very similar and consist of wheel-shaped hexanuclear [M6(µ-pymca)6(tmda)6]6+ cations, with pseudo-D…
First Dibenzophospholyl(diphenylphosphino)methane−Borane Hybrid P−(η2-BH3) Ligand: Synthesis and Rhodium(I) Complex
2009
The first dibenzophospholyl(diphenylphosphino)methane−borane hybrid ligand has been prepared from a Pd-catalyzed reaction of (chloromethyl)diphenylphosphine−borane with the dibenzophospholyl anion. This borane precursor is readily synthesized using a promising new reaction of diphenylphosphine−borane with dichloromethane, under phase transfer catalysis (PTC) conditions. The dibenzophospholyl(diphenylphosphino)methane−borane acts as a chelating P−(η2-BH3) ligand to afford an air-stable Rh(I) complex. The X-ray crystal structure of this complex shows complexation of both benzophospholyl and borane moieties.
Photo-assisted formation of a chelating diphos ligand from PPh3 and a cyclometallated [P(C6H4)(C6H5)2]− ligand. Crystal structure of Pd{η2-o-[P(C6H5)…
2000
Abstract The cyclometallated palladium compound, Pd[η2-(C6H4)P(C6H5)2]Br[P(C6H5)3] (1), in the solid state by action of light, evolves to give Pd{η2-o-[P(C6H5)2]2(C6H4)}Br2 (2). This compound contains the diphosphine, o-[P(C6H5)2]2(C6H4), as chelated ligand that is formed by a couple reaction of the metallated ligand η2-[(C6H4)P(C6H5)2]− and the coordinated arylphosphine. A study by NMR spectroscopy confirms that the o-phenylene bridge in the diphosphine ligand in 2 comes from the metallated phosphine ligand in 1.
Influence of the Nature of the Ligand on Dirhodium(II) Carbene Species: A Theoretical Analysis
2008
The influence of three prototypic families of bridging ligands (carboxylate, carboxamidate, and ortho-metalated arylphosphines) on the electronic structure of dirhodium(II) carbene complexes was theoretically analyzed. The calculations indicated that the electron donation of the ligand to the Rh atom, rather than the chelating ability or the metal−ligand orbital mixing, was responsible for tuning carbene charge via back-donation, which can influence the reactivity and selectivity of the dirhodium complexes in catalytic carbene transfer reactions.
Copper(II) and nickel(II) chelates with dihydrogen Trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate(2−) ion (H2CDTA2−). Synthesis, XRD structure a…
1996
Abstract Stoichiometric reactions of metal hydroxycarbonates with the acid trans -1,2-cyclohexanediaminotetraacetic acid (H 4 CDTA) in water under reduced pressure yielded [Cu(H 2 CDTA)]·H 2 O ( I ) and [Ni(H 2 CDTA) (H 2 O)]·4H 2 O ( II ). Both compounds were characterized by TG-DTA analysis, spectral properties (IR, reflectance and RSE) and X-ray diffraction. In I the copper(II) atom exhibits a distorted square-base coordination (type 4+1) by chelation of one H 2 CDTA 2− ligand through two N and two O (carboxylate) at the square base and one O (carboxylic) at the apex of the coordination polyhedron; a second carboxymethyl group of H 2 CDTA 2− remains free. In II the H 2 CDTA 2− chelating …
Treatment of hepatitis C virus infection with direct-acting antiviral drugs is safe and effective in patients with hemoglobinopathies
2017
Progression of liver fibrosis in patients with hemoglobinopathies is strongly related to the severity of iron overload and the presence of chronic hepatitis C virus (HCV) infection. Effective iron chelation therapy and HCV infection eradication may prevent liver complications. The European Association for the Study of the Liver guidelines recommend interferon-free regimens for the treatment of HCV infection in patients with hemoglobinopathies. However, data regarding the use of direct-acting antiviral drugs (DAAs) in this patient population are few. This observational study evaluated the safety and efficacy of therapy with DAAs in an Italian cohort of patients with hemoglobinopathies, chron…
Gadolinium-chelating nanogels as MR contrast agesnts specifically targeting tumor cells
2014
Development of multifunctional nanogels coordinating paramagnetic ions and displacing targeting ligands for preferential accumulation into tumors. Low molecular-weight Gd-chelates are widely used in clinical MRI for various purposes. However, these contrast agents (CAs) have several shortcomings: they rapidly extravasate from blood vessels to the interstitial space, have a short circulation times and show poor contrast at high magnetic fields. Incorporating gadolinium into flexible nanogels has the potential of increasing intravascular half-life, accumulation and retention in specific body compartments of the CA as well as increasing the MR signal, since many metal ions can be coordinated t…