Search results for "Protonation"
showing 10 items of 583 documents
Co-crystallization of Keggin type polyoxometalates [HL]3[PW12O40] and [Ln(DMF)8][PW12O40] (Ln=La, Dy, Yb) (L=N-(2-hydroxyphenyl)-3-methoxy-salicylide…
2016
Abstract Four new Keggin type polyoxometalate clusters [HL]3[PW12O40]·5MeOH (1) and [Ln(DMF)8][PW12O40] {Ln = La (2), Dy (3), Yb (4)} (L = N-(2-hydroxyphenyl)-3-methoxy-salicylideneamine) have been synthesized. Co-crystallization of complex 1 with each of the three complexes 2–4 takes place when the Schiff base ligand is treated with hydrated phosphotungstic acid, H3[PW12O40]·xH2O, hydrated lanthanide nitrate, Ln(NO3)3·6H2O in the presence of Ni(NO3)2·6H2O. The Schiff base ligand is protonated in complex 1 and thus it is neutralizing the charge of the polyoxotungstate anion, [PW12O40]3−. A dimethylformamide (DMF) coordinated trivalent lanthanide ion balances the negative charge of the polyo…
Control of the spin state by charge and ligand substitution: two-step spin crossover behaviour in a novel neutral iron(II) complex
2014
The influence of the charge and steric hindrance on the spin state of a series of four monomeric Fe-II complexes derived from the tridentate tigands 2-(1H-benzoimidazol-2-yl)-1,10-phenanthroline (Hphenbi) and 2-(1H-benzoimidazol-2-yl-9-methyl-1,10-phenanthroline (Hmphenbi) and their deprotonated forms (phenbi(-), mphenbi(-)) are investigated. The crystal structure and magnetic properties show that [Fe(Hphenbi)(2)](BF4)(2)center dot 1.5C(6)H(5)NO(2)center dot H2O (1) and its neutral form [Fe(phenbi)(2)]center dot 2CHCl(3)center dot H2O (2) are low-spin complexes at 400 K due to the strong ligand field imparted by the terpyridine-like tigand. In contrast, the steric hindrance induced by the m…
Coordination behaviour of methazolamide [N(-4-methyl-2-sulfamoyl-Δ2-1,3,4-thiadiazolin-5-ylidene)] acetamide, an inhibitor of carbonic anhydrase enzy…
1993
Abstract The interaction of methazolamide (Hmacm) with Ni(II) ion and ammonia molecules gives rise to the complex of formula [Ni(macm)2(NH3)4]. The complex crystallizes in the monoclinic P21/n space group with a = 14.255(4), b = 7.126(2), c = 12.444(3) A, β = 113.12(3)° and Z = 2. The structure was refined to R = 0.065 (Rw = 0.065). The complex consists of monomeric units which interact through hydrogen bonds and van der Waals contacts. The Ni(II) ion is coordinated with the deprotonated sulfonamido nitrogen of the macm− ligand in axial sites and the ammonia molecules in equatorial positions. IR, electronic spectra and 1H NMR results are also reported.
Protonation and methylation reactions of 2-pyridyl-palladium(II) and -platinum(II) complexes
1983
Abstract The reactions of strong acids HX and HClO4 with the 2-pyridyl complexes [PdX(μ-C5H4N-C2,N)(PPh3)]2 (X = Cl, Br), trans-[PdCl(C5H4N-C2)(PEt3)2] and [PdCl(C5H4N-C2)(dppe)] yield the N-protonated derivatives cis-[PdX2-(C5H5N-C2)(PPh3)], trans-[PdCl(C5H5N-C2)(PEt3)2]ClO4 and [PdCl-(C5H5N-C2)(dppe)]ClO4, respectively. The terminal 2-pyridyl group of trans-[PdCl(C5H4N-C2)(PEt3)2] and [PdCl(C5H4N-C2)(dppe)] also reacts with Me2SO4/NaClO4 to give trans-[PdClC5H4(l-Me)N-C2(PEt3)2]ClO4 and [PdClC5H4(l-Me)N-C2(dppe)]ClO4. Analogous N-protonation or N-methylation reactions occur with trans-[PtBr(C5H4N-C2)(L)2] (L = PEt3, PPh3). The complexes trans-[MX(C5H5N-C2)(PMe2Ph)2]ClO4 (M = Pd, X = Cl an…
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 …
NMR, potentiometric and ESI-MS combined studies on the zinc(II) magnesium(II) and calcium(II) complexation by (morpholin-1-yl)methane-1,1-diphosphoni…
2012
Abstract The crystal structures of the two derivatives of aminomethane-1,1-diphosphonic acid with morpholinyl- (1) and thiomorpholinyl- (2) side chains were determined by single crystal X-ray diffraction and discussed with respect to molecular geometry and solid state organization. The protonation equilibria, solution behavior and complex-formation equilibria in solutions of 1 and 2 with the Zn(II), Mg(II) and Ca(II) ions were studied by means of NMR, pH-potentiometry and ESI-MS methods. As the p K ( NH + ) protonation constants of 1 and 2 are high (11.65 and 11.91, respectively) two different approaches were used to evaluate the pH-potentiometric data. The first approach disregarded the pr…
A three-dimensional copper(ii) 12-metallacrown-4 complex with malonomonohydroxamic acid (H3mmh) as a ligand
2011
Slow diffusion of an ethanolic solution of copper(ii) into an aqueous solution of partially deprotonated malonodihydroxamic acid (H4mdh) affords the pentanuclear complex of formula {[K(H2O) 2]2[Cu5(mmh)4]}n (1) (H3mmh = malonomonohydroxamic acid) which is formed by 12-MC-4 metallacrown units with the fifth copper(ii) ion being placed at the center of the square metallacrown unit. The dianionic pentacopper(ii) planar entity interacts with diaquapotassium(i) counterions through the carboxylate-oxygen atoms resulting in a neutral three-dimensional structure. Magnetic susceptibility measurements in the temperature range 1.9-300 K for 1 show the occurrence of relatively strong antiferromagnetic …
New Reactivity of 4‐Amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole: Synthesis and Structure of a Mononuclear Species, a Dinuclear Species, and a Novel Te…
2007
Reactions of Ni(O 2 CMe) 2 ·4H 2 O or NiCl 2 ·6H 2 O, 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) and NaN 3 or KSCN in different molar ratios heated under reflux or hydrothermal conditions generate a mononuclear species with dimorphous phases, a dinuclear species incorporating an in situ deaminated [bpt-H] - ligand and a tetranuclear rectangle box incorporating an unprecedented μ:η 1 :η 2 :η 1 coordination mode of the deprotonated [abpt-H] - ligand. Structural analysis reveals that a pair of [Ni 2 (μ 1,1 -N 3 )(μ-OAc)] motifs in [Ni 4 (abpt) 2 -(abpt-H)(N3) 5 (Ο 2 CMe) 2 ]·5H 2 O (1) are bridged by two abpt and one [abpt-H] - units into a rectangle box. [Ni 2 (bpt-H) 2 -(SCN) 2 (H 2…
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). …
New complexes of nickel and nickel/cobalt with tetrahydrofuran-2,3,4,5-tetracarboxylic acid, THF(COOH)4. Crystal structures of Ni[THF(COOH)2(COOH)2](…
1993
Abstract The reaction of NiCl2·6H2O with tetrahydrofuran-2,3,4,5-tetracarboxylic acid, THF(COOH)4, partially deprotonated by Na2CO3 (1 : 1 metal/ligand molar ratio), yielded Ni[THF(COOH)2(COO)2](H2O)3 (1). The molecular structure of 1 was determined by X-ray diffraction on the monocrystal. The structure consists of a mononuclear neutral unit with the nickel atom coordinated by a [THF(COOH)2(COO)2]2− ligand, which acts as a tridentate ligand, and three water molecules. Direct interaction of NiCl2·6H2O and CoCl2·6H2O (1 : 1 molar ratio) with THF(COOH)4 previously deprotonated by Na2CO3 (1 : 1 metal/ligand molar ratio) gave, by slow evaporation of the solution obtained, green crystals of the n…