Search results for "deprotonation"

Outer and inner coordination sphere chemistry of polyazacyclophane platinum(II) complexes. Crystal structure of [PtBr4]2(H4L1) · H2O (L1 = 2,6,9,13-t…

1997

Abstract The interaction of PtCl42− with the new azaparacyclophane 2,5,8,11-tetraaza[12]paracyclophane (L2) has been studied by 1H, 13C and 195Pt NMR spectroscopy. Three different complexes are detected as a function of pH, all of them presenting cis-arrangement of nitrogen donors and chloride anions. In the first one, formed at acidic pH, the central nitrogen atoms of the macrocyclic are coordinating to Pt(II) while the benzylic nitrogens remain protonated. Deprotonation of these nitrogens brings about a reorganisation of the complex, and the platinum is then coordinated by one benzylic nitrogen and the consecutive nitrogen in the macrocycle. This process can be monitored by NMR. Finally, …

Preparation and reactions of palladium(II) complexes with C2-bonded heteroaromatic ligands trans[PdCl(RN)(PPh3)2] (RN = 2-pyridyl, 2-pirazyl, 2-pyrim…

1986

Abstract The complexes trans -[PdCl(R N )(PPh 3 ) 2 ] (I) [R N = 2-pyridyl (2-Py), 2-pyrazyl (2-pyz), 2-pyrimidyl (2-pym) group] have been prepared in high yield by deprotonation with NEt 3 of the corresponding cationic compounds trans [PdCl(R N H) (PPh 3 ) 2 ] + (R N H = N -protonated C 2 -heteroaromatic ligand) in the presence of an excess of PPh 3 . In chlorinated solvents, complexes I undergo a slow reversible dimerization into the binuclear derivatives [PdCl(μ-R N )(PPh 3 )] 2 (II) (μ-R N = C 2 , N 1 -bridging ligand). From the 31 P NMR spectra in 1,2-dichloroethane the following dissociation constants were obtained: 1.9 mol 1 −1 (R N = 2-py), 5.1 × 10 −2 (2-pym), 6.6 × 10 −3 (2-pyz). …

From C–S–H to C–A–S–H: Experimental study and thermodynamic modelling

2015

Abstract It has long been known that the stoichiometry of C–S–H varies with the calcium hydroxide concentration in solution. However, this issue is still far from understood. We revisit it in both experimental and modelling aspects. A careful analysis of the solubility confirms the existence of three different C–S–H phases, defined as Ca 4 H 4 Si 5 O 16 , Ca 2 H 2 Si 2 O 7 and Ca 6 (HSi 2 O 7 ) 2 (OH) 2 , respectively. The variation of the Ca/Si ratio of the three phases has been described by surface reactions: the increase of the Si content is accounted for by silicate bridging, the increase of calcium content and the surface charge are accounted for by reactions involving silanol groups v…

Microwave-Assisted Synthesis of Polysubstituted 4-Quinolones from Deprotonated α-Aminonitriles

2010

The α-alkylation of deprotonated N-aryl-α-aminonitriles with α-bromoesters furnishes intermediates that can be cyclized to 4-quinolones upon microwave irradiation. Alternatively, base-induced dehydrocyanation of the alkylation products furnishes enaminoesters, which can, for example, be converted into quinoline-3-carboxylates.

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)…

ChemInform Abstract: A Short Synthesis of Pyridines from Deprotonated α-Aminonitriles by an Alkylation/RCM Sequence.

2016

Cu(II), Ni(II) and Zn(II) mononuclear building blocks based on new polynucleating azomethine ligand : Synthesis and characterization

2017

Five new mononuclear complexes formed by the polynucleating ligand 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene]acetohydrazide (HL): [Ni(L)(HL)]ClO4·2CH3OH (1), [Ni(L)2]·CH3OH (2), [Zn(L)(HL)]ClO4·2CH3OH (3), [Zn(L)2]·CH3OH (4) and [Cu(L)2]·CH3OH (5) were synthesized and characterized by elemental analysis, mass-spectrometry, IR-spectroscopy and X-ray analysis. The complexes reveal distorted octahedral N4O2 coordination arrangement formed by both protonated and deprotonated (1, 3) or two deprotonated ligand molecules (2, 4, 5). The presence of non-coordinated oxime and pyrazole groups resulted in the formation of extensive systems of hydrogen bonds in the crystal…

Interaction of Dimethyltin(IV)2+ Cation with Gly-Gly, Gly-His, and Some Related Ligands. A New Case of a Metal Ion Able To Promote Peptide Nitrogen D…

1999

Equilibrium (pH-metric) and spectroscopic (1H,13C, and 119Sn NMR and 119Sn Mossbauer) studies were performed to characterize the interaction of the dimethyltin(IV) cation with glycine, glycyl-glycine (Gly-Gly), imidazole-4-acetic acid, histamine, histidine, glycyl-histamine, glycyl-histidine (Gly-His), and β-alanyl-histidine (carnosine). For histamine and glycyl-histamine (having only nitrogen donor atoms) no complex formation was detected. The hydrolyzed species of the dimethyltin(IV) cation are always dominant over the complexes formed with the other ligands, except with Gly-Gly and Gly-His. For these two ligands, {COO-,N-,NH2} coordinated complexes are dominant in the neutral pH range wi…

Synthesis, Characterization, and X-ray Crystal Structures of Cyclam Derivatives. 5. Copper(II) Binding Studies of a Pyridine-Strapped 5,12-Dioxocycla…

2004

The copper(II) binding properties of the macrobicyclic diamide 1,9,12,18,22-pentaazatricyclo[7.6.6.1(3,7)]docosa-3,5,7(22)-triene-13,19-dione (L1) have been fully investigated by spectroscopic (IR, UV-vis, EPR, MALDI-TOF MS), X-ray diffraction, potentiometric, electrochemical, and spectroelectrochemical methods. This constrained receptor possesses a hemispherical cavity created by cross-bridging the 1 and 8 positions of trans-dioxocyclam (1,4,8,11-tetraazacyclotetradecane-5,12-dione, L2) with a 2,6-pyridyl strap. Treatment of L1 with a copper salt in methanol produces a red complex of [Cu(L1H(-1))]+ formula in which the copper atom is embedded in a 13-membered ring and coordinated by both a…

Bis(oxamato)palladate(II) complexes: synthesis, crystal structure and application to catalytic Suzuki reaction

2015

New bis(oxamato)palladate(II) complexes, [Pd(H2O)4][Pd(2,6-Me2pma)2]·2H2O (1), (n-Bu4N)2[Pd(2,6-Me2pma)2]·2H2O (2a), and (n-Bu4N)2[Pd(2,6-Me2pma)2]·2CHCl3 (2b) (2,6-Me2pma = N-2,6-dimethylphenyoxamate and n-Bu4N+ = tetra-n-butylammonium), have been synthesized and the structures of 1 and 2b characterized by single-crystal X-ray diffraction. Complex 1 is a double salt constituted by tetraaquapalladium(II) cations and bis(oxamato)palladate(II) anions interlinked by hydrogen bonds. The palladium(II) ions in 1 are four-coordinate with two oxygens and two nitrogens from two fully deprotonated oxamate ligands (anion), and four water molecules (cation) building centrosymmetric square-planar surrou…