Search results for "HeLa"
showing 10 items of 738 documents
Titanium Complexes of Chelating Bis(phenolato) Ligands with Long Titanium−Sulfur Bonds. A Novel Type of Ancillary Ligand for Olefin Polymerization Ca…
1996
The sulfide-linked bis(phenol) tbmpH2 (tbmp = 2,2‘-thiobis(6-tert-butyl-4-methylphenolato)) gives a series of titanium complexes of the formula [Ti(tbmp)X2]2 or [Ti(tbmp)(L)X2] (L = two-electron ligand, X = one-electron ligand). The molecular structures of [Ti(tbmp)(OiPr)2]2 and of [Ti(tbmp){C6H4(CH2NMe2)-2}Cl] were determined by single-crystal X-ray structural analyses. An unusually long titanium−sulfur bond of ∼270 pm is observed in both complexes which contain a six-coordinate titanium center. Variable-temperature NMR spectroscopy shows a fluxional coordination of the chelating aryl group in [Ti(tbmp){C6H4(CH2NMe2)-2}Cl].
Heterocyclic systems containing antimony (III) -VIII . Hypervalency by intramolecular 1,5-chelation Sb · · · N in rings RSb [ (CH2) 3] 2NR′ (NR′ = NM…
1998
Abstract Eleven antimony compounds RSb [ (CH2) 3] 2 NR′ and eight germanium compounds R2Ge [ (CH2) 3] 2 NR′ (some combinations of R = Cl, I, NCS, OSiPh3, Ph, and NR′ = NMe, NBz, NBui) have been synthesized by diGrignard reactions and subsequent treatment with AgSCN, Ph3SiONa or PhLi. The compounds were compared to 14 Sn, 1 As, 5 Sb and 4 Bi analogues taken from the literature. Evidence is provided for 1,5-chelation Sb · · · N via crystal structure determinations (5+1 (lit) Sb compounds) , 13C- and 29Si-NMR chemical shifts, 12;Sb and 12;I Mossbauer data (11 and 3 Sb compounds, respectively) , cyclic voltammetry (9 Sb compounds) and semi-empirical MO calculations on the Extended Huckel level …
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 …