Search results for "coordination"
showing 10 items of 1282 documents
Copper(ii) and Zn(ii) coordination chemistry of tetraaza[n]cyclophanes
2003
The acid–base behaviour and Zn2+ and Cu2+ metal coordination chemistry of the novel orthocyclophane ligands 2,5,8,11-tetraaza[12]orthocyclophane (L2) and 2,5,9,12-tetraaza[13]orthocyclophane (L3) and metacyclophane 2,5,8,11-tetraaza[12]metacylophane (L1) are studied. Important differences in the chemistry of these compounds are found depending on the substitution of the aromatic ring. The ortho derivatives are much more basic in their first two protonation steps while the metacyclophane presents much larger constants in the third and fourth protonation stages. The crystal structure of the picrate salt of [H2L3]2+ shows an alternate disposition of the protons in the molecule with formation o…
Generation of [2×2] Grid Metallosupramolecular Architectures from Preformed Ditopic Bis(acylhydrazone) Ligands and through Component Self‐Assembly
2007
Ditopic bis(acylhydrazone) ligands, derived from the reactions of carbohydrazides with 2-phenylpyrimidine-4,6-dicarbaldehyde and designed for grid formation with octahedrally coordinating transition-metal ions, exhibit a varied coordination chemistry depending upon the degree of their deprotonation. The neutral acylhydrazones are relatively poor ligands and are seemingly involved in multiple, labile complexation equilibria varying with the solvent and the particular metal salt in solution; nevertheless, grid complexes of different forms can be isolated in the solid state. Although only limited study has been made of the singly deprotonated ligands, grid species appear to be much more readil…
Copper Complexes with Sulfonamides Derivatives of Natural Amino Acids as Chemical Nucleases
2007
Three new coordination compounds have been prepared by reacting copper salts with sulfonamides derived from amino acids. Their molecular structures have been determined with the aid of single crystal X-ray diffraction. The copper cations are four-coordinated in all cases and the local environment is almost planar. Compound [Cu(ts-gly)(NH3)2]·H2O (1) crystallizes in monoclinic space group P21/c (no 14) with Z = 4 and with unit cell parameters a = 6.0490(12) A, b = 24.719(5) A, c = 9.159(2) A, α = γ = 90°, and β = 94.69(3)°. Compound [Cu(ts-isoleu)(NH3)2] (2) crystallizes in monoclinic space group C2/c (no 8) with Z = 15 and with unit cell parameters a = 30.800(6) A, b = 6.5510(13) A, c = 15.…
Efficient Self-Assembly of Di-, Tri-, Tetra-, and Hexavalent Hosts with Predefined Geometries for the Investigation of Multivalency
2015
Coordination-driven self-assembly of differently shaped di- to hexavalent crown-ether host molecules is described. A series of [21]crown-7- and [24]crown-8-substituted bipyridine and terpyridine ligands was synthetized in a "toolbox" approach. Subsequent coordination to 3d transition metal and ruthenium(II) ions provides an easy and fast access to host assemblies with variable valency and pre-defined orientations of the crown-ether moieties. Preliminary isothermal calorimetry (ITC) titrations provided promising results, which indicated the host complexes under study to be suitable for the future investigation of multivalent and cooperative binding. The hosts described herein will also be su…
Straightforward synthesis of donor-stabilised phosphenium adducts from imidazolium-2-carboxylate and their electronic properties
2007
Cationic imidazolium-2-phosphanes were obtained by the addition of a chlorophosphane (R2PCl, R = Ph, iPr or Cy) to 1,3-dimethylimidazolium-2-carboxylate without the need for a purification step. An additional anion exchange reaction with KPF6 led to the corresponding halide-free ligands in excellent yields. The molecular structure of one of them was examined both in the solid state and in solution. The lone pair of electrons on the phosphorus atom is not delocalised to the imidazolium fragment and thus remains available for further metal coordination. As such compounds can be described as phosphenium cations stabilised by a N-heterocarbene donor base, the electronic properties of the Lewis …
Self-Assembly, Characterisation, and Crystal Structure of Multinuclear Metal Complexes of the [2×3] and [3×3] Grid-Type
2002
The self-assembly of new multimetallic complexes of grid-type architecture is described. The binding of a set of tris-terdentate ligands, 1 a-1 d, based on terpyridine-like subunits, with different octahedrally coordinated metal ions leads to the formation of species whose structure depends strongly on the ligand, the metal ion, the counterion, the solvent, and the reaction conditions. Under suitable conditions, the [3 x 3] grid was obtained from the reaction of ligand 1 a with zinc tetrafluoroborate and from ligand 1 b with mercury triflate. The other ligands led to the formation of mainly one compound of composition [M(6)L(5)](12+), which has the structure of an incomplete [2 x 3] grid. T…
ChemInform Abstract: Dynamic Magnetic MOFs
2013
In this review we combine the use of coordination chemistry with the concepts of molecular magnetism to design magnetic Metal–Organic Frameworks (MOFs) in which the crystalline network undergoes a dynamic change upon application of an external stimulus. The various approaches so far developed to prepare these kinds of chemically or physically responsive MOFs with tunable magnetic properties are presented.
Dual application of (aqua)(chlorido)(porphyrinato)chromium(III) as hypersensitive amine-triggered ON switch and for dioxygen activation.
2014
Although synthesis and substitution reactions of chlorido chromium(III) porphyrins Cr(III)(TPP)(Cl)(L) (H2TPP = 5,10,15,20-tetraphenyl porphyrin, L = pyridine, H2O, ROH, etc.), have been well-established in coordination chemistry for decades, an unexpected dichotomous reactivity of Cr(III)(TPP)(Cl)(H2O) (1) toward amines is disclosed here. This reactivity leads to the application of 1 as highly sensitive substoichiometric and irreversible ON switch for amine detection by an autocatalytic pathway. The concomitant activation of O2 by the 1/amine system is furthermore exploited in an electrochemically driven epoxidation of norbonene using O2 as initial oxidant.
Fragmentation reactions of realgar caused by early transition metal hydrides
2012
Abstract The reaction of realgar with [Cp′2MH3] in boiling toluene gave [Cp′2M2As2S6] (Cp′ = t-BuC5H4; M = Nb: 1; Ta: 2), while [Cp2WH2] (Cp = C5H5) reacted with As4S4 to give [Cp2W(H)(η1-As5S2)] (6). The structures were determined by X-ray crystallography. Compounds 1 and 2 are dimers in which two Cp′M units are symmetrically bridged by a μ,η2:2-AsS3 ligand, a sulfide ligand and a heteroallylic μ,η2:2-AsS2 ligand. The structure of 6 belongs to the type of bent metallocenes in which tungsten is surrounded tetrahedrally by two Cp ligands, a crystallographically found hydride atom and the new As5S2 cage. The reaction of 1 with W(CO)5THF gave [Cp′2Nb2As2S6·W(CO)5] (3) and [Cp′2Nb2As2S6W(CO)3·W…
Copper(II) complexes with sulfonamides derived from 2-picolylamine and their use as chemical nucleases
2006
Reaction between 2-picolylamine (2-aminomethylpyridine) with 2-mesitylenesulfonyl and 4- tert -butylbenzene sulfonyl chlorides leads to the formation of 2,4,6-trimethyl- N -[pyridin-2-ilmethyl]benzenesulfonamide (Hpmesa) and 4-ter-butyl- N -[pyridin-2-ilmethyl]benzenesulfonamide (Hptbsa). These compounds react with Cu(II) salts to yield coordination compounds with CuL 2 stoichiometry. The immediate environment of the metal ion is a highly distorted tetrahedron, the sulfonamide ligands acting in a bidentate fashion. Compound Hpmesa crystallizes in monoclinic space group P 2 1 /c (number 14), with Z = 4; complex [Cu(pmesa) 2 ] crystallizes in monoclinic space group P 1 ¯ (number 2), with Z …