Crystal structure of dichlorido-1κCl,2κCl-(μ2-3,5-dimethyl-1H-pyrazolato-1κN 2:2κN 1)(3,5-dimethyl-1H-pyrazole-2κN 2){μ-2-[(2-hydroxyethyl)amino-1κ2 N,O]ethanolato-1:2κ2 O:O}dicopper(II)

The title compound, [Cu2(C5H7N2)(C4H10NO2)Cl2(C5H8N2)], is a pyrazolate aminoalcohol complex which contains two dimethylpyrazole molecules in monodentate and bidentate-bridged coordination modes and a monodeprotonated diethanolamine molecule. Both copper atoms are involved in the formation of non-planar five-membered chelate rings. One Cu atom is in a distorted tetrahedral environment formed by the pyridine nitrogen atom of the protonated dimethylpyrazole molecule, the N atom of the deprotonated bridged dimethylpyrazole, the Cl atom and the bridged O atom of the monodeprotonated diethanolamine. The second Cu atom has an intermediate environment between trigonal bipyramidal and square pyramidal, formed by the N atom of the deprotonated bridged dimethylpyrazole, the Cl atom and the N atom of the aminoalcohol, and two O atoms of the deprotonated and protonated OH groups. In the crystal, N—H...Cl hydrogen bonds link the molecules into antisymmetric chains running along the a-axis direction. Adjacent chains are connected by O—H...O hydrogen bonds involving the hydroxyl group as donor.

Diaquabis{μ-1,5-bis[(pyridin-2-yl)methylidene]carbonohydrazide(1–)}di-μ-chlorido-tetrachloridotetrazinc(II)

A tetranuclear ZnII complex, [Zn4(C13H11N6O)2Cl6(H2O)2] or {[Zn2(HL)(H2O)(Cl2)](μCl)2[Zn2(HL)(H2O)(Cl)]}2, was synthesized by mixing an equimolar amount of a methanol solution containing ZnCl2 and a methanol solution containing the ligand H2 L [1,5-bis(pyridin-2-ylmethylene)carbonohydrazide]. In the tetranuclear complex, each of the two ligand molecules forms a dinuclear unit that is connected to another dinuclear unit by two bridging chloride anions. In each dinuclear unit, one ZnII cation is pentacoordinated in a N2OCl2 in a distorted square-pyramidal geometry, while the other ZnII cation is hexacoordinated in a N3OCl2 environment with a distorted octahedral geometry. The basal plane around the pentacoordinated ZnII cation is formed by one chloride anion, one oxygen atom, one imino nitrogen atom and one pyridine nitrogen atom with the apical position occupied by a chloride anion. The basal plane of the hexacoordinated ZnII cation is formed by one chloride anion, one hydrazinyl nitrogen atom, one imino nitrogen atom and one pyridine nitrogen atom with the apical positions occupied by a water oxygen atom and a bridged chloro anion from another dinuclear unit, leading to a tetranuclear complex. A series of intramolecular C—H...Cl hydrogen bonds is observed in each tetranuclear unit. In the crystal, the tetranuclear units are connected by intermolecular C—H...Cl, C—H...O and N—H...O hydrogen bonds, forming a planar two-dimensional structure in the ac plane.

A solid solution of ethyl and d 3-methyl 2-[(4-methylpyridin-2-yl)amino]-4-(pyridin-2-yl)thiazole-5-carboxylate

The synthesis of ethyl 2-[(4-methylpyridin-2-yl)amino)-4-(pyridin-2-yl)thiazole- 5-carboxylate via the Hantzsch reaction and partial in situ transesterification during recrystallization from methanol-d 4 to the d 3-methyl ester, resulting in the title solid solution, ethyl 2-[(4-methylpyridin-2-yl)amino)-4-(pyridin-2-yl)thiazole-5-carboxylate–d 3-methyl 2-[(4-methylpyridin-2-yl)amino)-4-(pyridin-2-yl)thiazole-5-carboxylate (0.88/0.12), 0.88C17H16N4O2S·0.12C16D3H11N4O2S, is reported. The refined ratio of ethyl to d 3-methyl ester in the crystal is 0.880 (6):0.120 (6). The pyridine ring is significantly twisted out of the plane of the approximately planar picoline thiazole ester moiety. N—H...N hydrogen bonds between the secondary amino group and the pyridine nitrogen atom of an adjacent symmetry-related molecule link the molecules into polymeric hydrogen-bonded zigzag tapes extending by glide symmetry in the [001] direction. There is structural evidence for intramolecular N...S chalcogen bonding and intermolecular weak C—H...O hydrogen bonds between adjacent zigzag tapes.

Crystal structure of (15,20-bis(2,3,4,5,6-pentafluorophenyl)-5,10-{(4-methylpyridine-3,5-diyl)bis[(sulfanediylmethylene)[1,1′-biphenyl]-4′,2-diyl]}porphyrinato)nickel(II) dichloromethane x-solvate (x > 1/2)

The title compound, [Ni(C64H33F10N5S2)]·xCH2Cl2, consists of discrete NiII porphyrin complexes, in which the five-coordinate NiII cations are in a distorted square-pyramidal coordination geometry. The four porphyrin nitrogen atoms are located in the basal plane of the pyramid, whereas the pyridine N atom is in the apical position. The porphyrin plane is strongly distorted and the NiII cation is located above this plane by 0.241 (3) Å and shifted in the direction of the coordinating pyridine nitrogen atom. The pyridine ring is not perpendicular to the N4 plane of the porphyrin moiety, as observed for related compounds. In the crystal, the complexes are linked via weak C—H...F hydrogen bonds into zigzag chains propagating in the [001] direction. Within this arrangement cavities are formed, in which highly disordered dichloromethane solvate molecules are located. No reasonable structural model could be found to describe this disorder and therefore the contribution of the solvent to the electron density was removed using the SQUEEZE option in PLATON [Spek (2015). Acta Cryst. C71, 9–18].

Crystal structures of two CuII compounds: catena-poly[[chloridocopper(II)]-μ-N-[ethoxy(pyridin-2-yl)methylidene]-N′-[oxido(pyridin-3-yl)methylidene]hydrazine-κ4 N,N′,O:N′′] and di-μ-chlorido-1:4κ2 Cl:Cl-2:3κ2 Cl:Cl-dichlorido-2κCl,4κCl-bis[μ3-ethoxy(pyridin-2-yl)methanolato-1:2:3κ3 O:N,O:O;1:3:4κ3 O:O:N,O]bis[μ2-ethoxy(pyridin-2-yl)methanolato-1:2κ3 N,O:O;3:4κ3 N,O:O]tetracopper(II)

Two CuII complexes [Cu(C14H13N4O2)Cl] n , I, and [Cu4(C8H10NO2)4Cl4] n , II, have been synthesized. In the structure of the mononuclear complex I, each ligand is coordinated to two metal centers. The basal plane around the CuII cation is formed by one chloride anion, one oxygen atom, one imino and one pyridine nitrogen atom. The apical position of the distorted square-pyramidal geometry is occupied by a pyridine nitrogen atom from a neighbouring unit, leading to infinite one-dimensional polymeric chains along the b-axis direction. Each chain is connected to adjacent chains by intermolecular C—H...O and C—H...Cl interactions, leading to a three-dimensional network structure. The tetranuclear complex II lies about a crystallographic inversion centre and has one core in which two CuII metal centers are mutually interconnected via two enolato oxygen atoms while the other two CuII cations are linked by a chloride anion and an enolato oxygen. An open-cube structure is generated in which the two open-cube units, with seven vertices each, share a side composed of two CuII ions bridged by two enolato oxygen atoms acting in a μ3-mode. The CuII atoms in each of the two CuO3NCl units are connected by one μ2-O and two μ3-O atoms from deprotonated hydroxyl groups and one chloride anion to the three other CuII centres. Each of the pentacoordinated CuII cations has a distorted NO3Cl square-pyramidal environment. The CuII atoms in each of the two CuO2NCl2 units are connected by μ2-O and μ3-O atoms from deprotonated alcohol hydroxy groups and one chloride anion to two other CuII ions. Each of the pentacoordinated CuII cations has a distorted NO2Cl2 square-pyramidal environment. In the crystal, a series of intramolecular C—H...O and C—H...Cl hydrogen bonds are observed in each tetranuclear monomeric unit, which is connected to four tetranuclear monomeric units by intermolecular C—H...O hydrogen bonds, thus forming a planar two-dimensional structure in the (\overline{1}01) plane.

Nucleophilic Attack at the Pyridine Nitrogen Atom in a Bis(imino)pyridine System: The Local Hard and Soft Acids and Bases Principle Perspective

Motivated by the unprecedented nucleophilic attack at the pyridine nitrogen atom in bis(imino)pyridines, observed by Gambarotta <em>et al.</em> and Gibson <em>et al.</em>, and the fact that normally pyridine undergoes reactions with electrophiles at its nitrogen atom, we applied the local hard and soft acids and bases principle to assert that nucleophilic attack at pyridine nitrogen atom depends fundamentally on stereoelectronic factors.

Fabrication of PEBA/Cu2O mixed-matrix membranes and their application in pyridine recovery from aqueous solution

The lone pair of electrons of the pyridine nitrogen atom can form a complex with some metal ions such as Cu+, Ag+, etc.

Indolizines and pyrrolo[1,2-c]pyrimidines decorated with a pyrimidine and a pyridine unit respectively

The three possible structural isomers of 4-(pyridyl)pyrimidine were employed for the synthesis of new pyrrolo[1,2-c]pyrimidines and new indolizines, by 1,3-dipolar cycloaddition reaction of their corresponding N-ylides generated in situ from their corresponding cycloimmonium bromides. In the case of 4-(3-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine the quaternization reactions occur as expected at the pyridine nitrogen atom leading to pyridinium bromides and consequently to new indolizines via the corresponding pyridinium N-ylides. However, in the case of 4-(2-pyridyl)pyrimidine the steric hindrance directs the reaction to the pyrimidinium N-ylides and, subsequently, to the formation of the pyrrolo[1,2-c]pyrimidines. The new pyrrolo[1,2-c]pyrimidines and the new indolizines were structurally characterized through NMR spectroscopy. The X-ray structures of two of the starting materials, 4-(2-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine, are also reported.

A Novel Pathway to Imidazo[1,2-a]pyridines. Access through Imino Pyridinium Salts

A new synthetic strategy for the preparation of imidazo[1,2-a]pyridines 10 is reported, which is based on the electrocyclization reaction of imino pyridinium salts 7 upon treatment with a strong base. The starting materials are easily prepared from 2-aminopyridine (3) by imine condensation and subsequent alkylation at the pyridine nitrogen atom. The ring closure reaction of the zwitterionic intermediate 8 to give a five-membered ring proceeds in low yield forming first the dihydro compound 9, which under the reaction conditions is transformed into the corresponding aromatic compounds 10 and 11 by air oxidation. The mechanism of the electrocyclization reaction is interpreted in detail by quantum-chemical calculations.

Palladium(II) and Platinum(II) Complexes of N-3-Pyridinylmethanesulfonamide

The complexes cis-[Pd(PMSA)2Cl2] cis-[Pt(PMSA)2X2], trans-[Pt(PMSA)2I2] and [Pt(PMSA)4]Cl2 (PMSA = N-3-pyridinylmethanesulfonamide; X = Cl, Br, I) have been synthesized and characterized by elemental analysis, molar electric conductivity, IR and 1H NMR spectra. A detailed assignment of the IR spectra (4000-150 cm-1) of the complexes, supported by an approximate normal coordinate analysis, has been performed. The complexes are of square-planar type and the PMSA ligand is coordinated via the pyridine nitrogen atom.