Search results for "Protonation"
showing 10 items of 583 documents
Di‐ and Trivalent Ytterbium Complexes Containing Linked Amino‐ and Amidocyclopentadienyl Ligands
2003
Reactions of the aminocyclopentadienes (C5Me4H)SiMe2NHR (R = Et, allyl, nPr, tBu) with [YbI2(THF)2] in the presence of two equivalents of potassium 1,2-diphenylethenide in THF at room temperature gave the diamagnetic half-sandwich complexes [Yb(η5-C5Me4SiMe2NHR)Ln(μ-I)]2 (L = THF, n = 2, L = DME, n = 1). The tert-butylamido derivative [Yb(η5-C5Me4SiMe2NHtBu)(THF)2(μ-I)]2 was characterized by X-ray structural analysis as a dinuclear complex containing a nonchelating aminocyclopentadienyl ligand. Deprotonation of the aminocyclopentadiene (C5H4tBu)SiMe2NHtBu with two equivalents of potassium 1,2-diphenylethenide in THF, followed by reaction with [YbI2(THF)2] at 60 °C, gave the trivalent ytterb…
Copper(II) complexes of quinoline polyazamacrocyclic scorpiand-type ligands: X-ray, equilibrium and kinetic studies
2012
The formation of Cu(II) complexes with two isomeric quinoline-containing scorpiand-type ligands has been studied. The ligands have a tetraazapyridinophane core appended with an ethylamino tail including 2-quinoline (L1) or 4-quinoline (L2) functionalities. Potentiometric studies indicate the formation of stable CuL(2+) species with both ligands, the L1 complex being 3-4 log units more stable than the L2 complex. The crystal structure of [Cu(L1)](ClO(4))(2)·H(2)O shows that the coordination geometry around the Cu(2+) ions is distorted octahedral with significant axial elongation; the four Cu-N distances in the equatorial plane vary from 1.976 to 2.183 Å, while the axial distances are of 2.27…
Stability and kinetics of the acid-promoted decomposition of Cu(II) complexes with hexaazacyclophanes: kinetic studies as a probe to detect changes i…
2004
The synthesis, protonation and Cu(II) coordination features of the novel azacyclophane type receptors 2,6,10,13,17,21-hexaza[22]-(2,6)-pyridinophane (L2), 2,6,9,12,15,19-hexaza[20]-(2,6)-pyridinophane (L5) and 2,6,9,12,15,19-hexaza[20]metacyclophane (L6) are presented. The protonation and Cu(II) constants are analysed and compared with the previously reported open-chain polyamines 4,8,11,15-tetrazaoctadecane-1,18-diamine (L1) and 4,7,10,13-tetraazahexadecane-1,16-diamine (L4) and of the cyclophane 2,6,10,13,17,21-hexaaza[22]paracyclophane (L3). All the systems form mono- and dinuclear complexes whose stability and pH range of existence depend on the type of hydrocarbon chains and molecular …
Zirconocene complexes bearing novel 3-dimethylamino-1,2-dihydropentalene derived ligand systems.
2010
Coupling of the N,N-dimethylacrylamides 6a-c with cyclopentadienide resulted in the formation of the substituted 3-dimethylamino-1,2-dihydropentalnenes 2a-c. Deprotonation followed by metallation with CpZrCl(3)·DME gave the substituted zirconocenes 12a-c. The reaction of 3-dimethylamino-1-methyl-dihydropentalene 2a with ZrCl(2)(NMe(2))(2)·2THF resulted in a unique coupling between a pair of the aminodihydropentalene derivatives to yield an unsymmetrically bridged novel ansa-zirconocene framework (9a). Treatment of the 1,1-dimethyl-substituted substrate 2b with this Zr-amido reagent in contrast resulted in a clean deprotonation and formation of the unbridged bis(dimethylaminohydropentalenyl)…
Proton and Electron Transfer to a Polymer‐Supported Nitrido Molybdenum(VI) Complex
2013
Invited for the cover of this issue is the group of Katja Heinze at Johannes Gutenberg University of Mainz, Germany. The cover image shows the reactive imido molybdenum(V) intermediate that has been obtained by protonation followed by reduction of the nitrido molybdenum(VI) precursor anchored to a polymeric environment.
Heterometallic Pentanuclear [Ni 4 Ln] (Ln III = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions
2014
The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square-antiprism geometry. All the NiII ions are connected to the central LnIII ion through μ2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxy…
The crystal structure and magnetic properties of 3-pyridinecarboxylate-bridged Re(ii)M(ii) complexes (M = Cu, Ni, Co and Mn)
2015
The novel Re(II) complex NBu4[Re(NO)Br4(Hnic)] (1) and the heterodinuclear compounds [Re(NO)Br4(μ-nic)Ni(dmphen)2]·½CH3CN (2), [Re(NO)Br4(μ-nic)Co(dmphen)2]·½MeOH (3), [Re(NO)Br4(μ-nic)Mn(dmphen)(H2O)2]·dmphen (4), [Re(NO)Br4(μ-nic)Cu(bipy)2] (5) [Re(NO)Br4(μ-nic)Cu(dmphen)2] (5') (NBu4(+) = tetra-n-butylammonium cation, Hnic = 3-pyridinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline, bipy = 2,2'-bipyridine) have been prepared and the structures of 1-5 determined using single crystal X-ray diffraction. The structure of 1 consists of [Re(NO)Br4(Hnic)](-) anions and NBu4(+) cations. Each Re(II) is six-coordinate with four bromide ligands, a linear nitrosyl group and a nitrogen ato…
Interaction of Zn(II) and Cd(II) with Large Polyazacycloalkanes in dmso/H2O (80:20 vol./vol.). A potentiometric Study.
1990
Abstract A potentiometric study on the interaction at 25 °C and 0.15 mol dm −3 between large polyazacycloalkanes of the series [3 k ]aneN k and Zn(II) and Cd(II) ions in dmso:H 2 O (80:20 vol./vol.) is reported. The protonation behavior of the free macrocycles and coordination trends are compared with those previously observed in aqueous solution. The main features observed in the mixed solvent are: similar protonation behavior of the free polyamines, greater tendency to form binuclear and protonated complexes and a lower tendency to bear hydrolytic reactions.
Untersuchungen zur Konfigurationsstabilität von Enolaten aus β‐Ketocarbonsäureestern
1988
Z- und E-Enole von β-Ketocarbonsaurederivaten 1a–c werden vollstandig und irreversibel deprotoniert, wobei unter Konfigurationserhalt (kinetische Kontrolle) die Enolate 2a–c entstehen. Abhangig von Gegenionen (Li, Na, K), Medium (THF, HMPT) und Temperatur kann anschliesend eine Z/E-Aquilibrierung eintreten. Auf dieser Basis last sich die Synthese von Enolethern und Enolestern auf die gewunschte Konfiguration hinsteuern. Investigations on the Stability of the Configuration of Enolates from β-ketocarboxylic Acid Esters Z- and E-enoles of β-ketocarboxylic acid esters 1a–c are completely and irreversibly deprotonated yielding the enolates 2a–c under retention of the configuration (kinetic contr…
Equilibrium and Kinetic Properties of Cu II Cyclophane Complexes: The Effect of Changes in the Macrocyclic Cavity Caused by Changes in the Substituti…
2008
The o-B232, m-B232 and p-B232 cyclophanes result from attaching the terminal amine groups of 1,4,8,11-tetraazaundecane (232) to the benzylic carbons of the corresponding o-, m- or p-xylanes. The cavity size of these cyclophanes changes moderately as a consequence of the substitution at the aromatic ring. The effects caused by these changes on the equilibrium constants for protonation and CuII complex formation of the cyclophanes are analyzed and compared with those of the noncyclic 232 polyamine. All three cyclophanes form mononuclear complexes, but only o-B232 is able to coordinate to CuII through the four amine groups simultaneously, whereas m-B232 and p-B232 can only use three nitrogen d…