N-butyl-,N-iso-butyl-andN-sec-butyl-2-picolinamineN-oxide complexes derived from copper(II) salts of polyatomic anions

Summary N-butyl-,N-iso-butyl- andN-sec-butyl-2-picolinamineN- oxide complexes have been prepared from copper(II) perchlorate, tetrafluoroborate and nitrate. Violet solids were isolated from the first two salts while complexes isolated from the nitrate salt were blue green or blue. The ligands coordinatevia both theN-oxide oxygen and the amine nitrogen to give bis (ligand) complexes and only in the case of the nitrate solids is there interaction between the copper(II) centre and the polyatomic anion. Resolution of the g feature in the powder spectra of several of these complexes results from the bulkiness of the butyl groups and therefore dilution of the copper(II) centers. In comparison to the previously studied 2 picolinamineN-oxides with lower alkyl substituents, the complexes have stronger in-plane bonding by the ligands.NATO Fellow on leave from Istanbul Medical Faculty, Istanbul University.     

Cu(II) complexes of N-propyl-2-picolinamine N-oxide

Cu(II) complexes have been prepared with N-propyl-2-picolinamine N-oxide(PA) employing the perchlorate, tetrafluoroborate, nitrate, chloride and bromide salts. The following unique solids have been isolated and characterized: Cu(PA)₂X₂ (X = ClO₄^?, BF₄^? and NO₃^?) and Cu(PA)X₂ (X = Cl^?, Br^?). Characterization has been accomplished primarily by IR, electronic and ESR measurements of the solid state since considerable alteration of the complexes occurs on dissolution. PA bonds as a bidentate ligand via its N-oxide oxygen and amine nitrogen in all of the complexes. Anion coordination occurs in the halogen complexes and the nitrate ions appear to be bound to Cu(II) as monodentate ligands in Cu(PA)₂(NO₃)₂. In addition, there appears to be a rhombic distortion of the CuO₂N₂ chromophore of the perchlorate and tetrafluoroborate solids which is probably due to the steric requirements of the propyl substituents.     

Polymerization of 2-Oxazolines. IV. The Structure and the Reactivity of 2-Substituted-2-oxazolines and Oxazolinium Perchlorates

Abstract

In order to elucidate the structure and the stability of the growing cationic end in the polymerization of 2-oxazolines, the reactions of 2-bromoethylbenzamide with silver salts such as silver perchlorate, tetrafluoroborate, nitrate, nitrite, cyanate, and acetate were investigated. The reactions with silver perchlorate and tetrafluoroborate gave the 2-phenyl-2-oxazolinium salt (intramolecular O-alkylation product) quantitatively, whereas the reaction with silver nitrate gave the corresponding alkyl nitrate (staight-chain product). For the reactions with silver nitrite, cyanate and acetate, both products were obtained. In order to elucidate the ring-opening reactivity of the oxazolinium cation, the ring-opening addition reaction of N-methyl-2-oxazolinium perchlorates with pyridine was investigated. It was found that N-methyl-2-phenyl-2-oxazolinium perchlorate was more reactive toward the nucleophilic ring-opening reaction than was N-methyl-2-methyl-2-oxazolinium perchlorate. The mutual copolymerization of 2-phenyl-2-oxazoline with the other 2-substituted-2-oxazoline such as 2-methyl-, 2-isopropyl-, and 2-benzyl-2-oxazoline indicated that the monomer reactivity ratio r₂ was much larger than unity, whereas r₁ was very much smaller. Based on these results, the influence of the structure and the reactivity of the monomer and the growing cationic end of the polymerizability of 2-oxazolines are discussed.     

Transition metal complexes of 2-Carbethoxypyridine (Ethyl picolinate)

Summary A variety of metal(II) complexes of 2-carbethoxypyridine (L) have been prepared and characterised. With metal(II) chlorides the bis complexes can be formulated [ML₂Cl₂]^o (M=Cu^II, Ni^II, Co^II, Fe^II or Mn^II). The complexes are six-coordinate with 2-carbethoxypyridine acting as a bidentate ligandvia the pyridine nitrogen and the carbonyl group of the ester. The chloro complexes are nonelectrolytes in nitroethane; magnetic susceptibility measurements, i.r. and d-d electronic spectra are reported. With metal(II) perchlorate salts the complexes can be formulated as six-coordinate [ML₂ (OH₂)₂] [ClO₄]₂ species containing ionic perchlorate. The ester exchanges of some of these complexes with a variety of primary alcohols have been investigated.     

Nickel(II) complexes of a thiosemicarbazone prepared from 2-Acetylpyridine

Summary The ligand 3-azabicyclo[3.2.2]nonane-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide (HL), which is observed in an unusual tautomeric form in the solid state, and its selenium analogue (HLSe) have been used to prepare a series of nickel(II) complexes. Compounds of the general formula [NiLX] (X=Cl, Br, NCS, N₃, NO₂ or NCSe) as well as [Ni(LSe)Cl] have been found to be diamagnetic, planar complexes. A single crystal study of [NiL(NCS)] shows the deprotonated ligand bound in a tridentate mannervia its pyridyl nitrogen, imine nitrogen and the thione sulphur atom with the nitrogen atom of the thiocyanato-ligand occupying the fourth coordination position. The solids prepared from the nickel(II) salts having tetrafluoroborate, nitrate and iodide ions approximate to octahedral symmetry and have neutral HL ligands coordinated in a bidentate fashionvia the pyridine and imine nitrogens with the remaining coordination sites being occupied by the anions or water molecules. The [NiL₂] solid is also octahedral with the two deprotonated ligands bonding as tridentate groupsvia the same atoms as in the [NiLX] complexes.     

Iron(III) complexes of some thiosemicarbazones derived from 2-acetylpyridine,its 6-methyl derivative and itsN-oxide

Summary A series of iron(III) complexes of thiosemicarbazones derived from 2-acetylpyridine, 6-methyl-2-acetylpyridine and 2-acetylpyridineN-oxide have been prepared from Fe(ClO₄)₃ and FeCl₃. All of the isolated solids have cations involving two monobasic tridentate ligands, and either perchlorate or tetrachloroferrate(III) anions and are 11 electrolytes. Coordinationvia the pyridine nitrogen (or theN-oxide oxygen), the imine nitrogen and the sulphur atom are confirmed by infrared spectra and x-ray diffraction. The presence of two different iron(III) species is indicated by the electron spin resonance spectra of the tetrachloroferrate(III) solids. E.s.r. along with electronic spectra prove the spin-paired configuration of these cationic iron(III) complexes.NATO Fellow, on leave from Istanbul Medical Faculty, Istanbul University.     

2-Amino-3-picolineN-oxide complexes formed from various copper(II) Salts

Summary Copper(II) complexes of 2-amino-3-picolineN-oxide (3 MA) have been isolated as perchlorate, tetrafluoroborate, nitrate, chloride and bromide salts, and characterized by spectral methods (i.e., i.r., u.v.-vis and e.s.r.). Variation of the ligand to copper(II) salt ratio yielded solids having the following empirical formulas: Cu(3 MA)₄X₂ (X = ClO₄, BF₄ or NO₃), Cu(3 MA)₂X₂ (X = NO₃, Cl or Br) and Cu(3 MA)X₂ (X = Cl). In addition, a deprotonated ligand complex, Cu(3 MA-H)₂, was prepared by treating an aqueous slurry of Cu(3 MA)₄(ClO₄)₂ with NaOH. This complex is considered to be square planar, but does associate to form a dimer in nonpolar solvents such as CHCl₃. The complexes involving coordinated anions appear to be polymeric and to contain halogen orN-oxide oxygen bridging ligands.     

Differences in the coordinating ability of water,perchlorate and tetrafluoroborate toward copper(I). The x-ray crystal structures of [Cu(1,4-thioxane)3OClO3], [Cu(1,4-thioxane)3OH2]BF4 and [Cu(1,4-thioxane)4BF4

Summary Crystal structure determinations of the non-isomorphous salts, Cu(1,4-thioxane)₃(ClO₄) and Cu(1,4-thioxane)₄(BF₄) were carried out. The former compound was shown to contain strongly coordinated perchlorate while the later contains ionic tetrafluoroborate. For the coordinated perchlorate group, Cu-O is 2.278(8) Å. A third compound, Cu(1,4-thioxane)₃(H₂O)(BF₄), was also characterized by x-ray crystallography, and contains a coordinated water molecule (with Cu-O 2.234(7) Å) that is hydrogen bonded to ionic tetrafluoroborate. All three complexes have approximately tetrahedral geometry. The copper(I) atom is coordinated to the sulfur atoms of the 1,4-thioxane rings. In each of the complexes, one of the 1,4-thioxane six-membered rings is coordinatedvia an equatorial ring position and the remaining two or three rings are coordinatedvia an axial position. The compound, Cu(1,4-thioxane)₄(ClO₄), was also prepared and found to be isomorphous with Cu(1,4-thioxane)₄ (BF₄), enabling a comparison to be made between the i.r. spectra of ionic and coordinated perchlorate in similar complexes.     

Reaction of 2-(arylazo)pyridine complexes of type [OsX2L2] (X = Cl or Br) with heterocyclic bases (B): spectra and electrochemistry of [OsX(B)L2]ClO4·H2O

Summary The synthesis and characterization of a series of complexes of the type [OsX(B)L₂] ⁺ (X = Cl or Br, B = pyridine (py) and pyrazine (pyz), L = 2-(phenylazo)pyridine (L¹) or 2-(m-tolylazo)pyridine (L²)) is described. The cations have been isolated as crystalline perchlorate monohydrates after purification by column chromatography. The diamagnetic compounds display several spin-allowed and spin-forbidden m.l.c.t. transitions in the visible region. The metal-centred oxidations and ligand-based reductions of the complexes are studied electrochemically in MeCN. Two consecutive one-electron oxidations corresponding to Os^III/Os^II and Os^IV/Os^III couples occur at ca. 1.3 and ca. 2.3 V versus s.c.e. respectively. Four successive azo-reductions are observable in the potential range -0.4 to -2.4V.     

Bis(2-(1H-imidazol-2-yl)-pyridine)copper(II): Effects of counteranions on the molecular and supramolecular structures

The synthesis and physical properties of bis(2-(1H-imidazol-2-yl)-pyridine)copper(II) with chloride, nitrate and perchlorate as counteranions have been described. Microanalysis, magnetic susceptibility, conductivity and various spectroscopic measurements have been used for the characterization of the complexes. The crystal structures of all three complexes have been determined. Intermolecular hydrogen-bonding interactions and the resulting self-assembly patterns for each of the species have been scrutinized. The chloride containing complex crystallizes as a trihydrate, where the metal ion is in a tetragonally elongated cis-N₄Cl₂ coordination sphere. This complex provides a three-dimensional honeycomb-like structure through N–H?Cl, O–H?Cl and O–H?O hydrogen bonds. In the nitrate containing species, one of the two counteranions coordinates to the metal centre to provide an irregular N₄O₂ coordination sphere, while the other counteranion, with the help of a lattice water molecule, assembles a ladder-like structure via N–H?O and bifurcated O–H?O,O hydrogen bonds. A one-dimensional polymeric species has been formed when perchlorate is the counteranion. Here one of the two perchlorates acts as a bridge between the metal centres that are in tetragonally elongated trans-N₄O₂ coordination spheres. This polymeric chain, together with the second perchlorate and a water molecule, form a ribbon-like structure due to N–H?O and O–H?O hydrogen bonds.     

2-amino-4,6-lutidineN-oxide complexes formed from various copper(II) salts

Summary Copper(II) complexes of 2-amino-4,6-lutidineN-oxide (4,6DMAH) have been isolated as tetrafluoroborate, nitrate, chloride and bromide salts, and characterized by spectral methods (i.e., i.r., u.v.-vis. and e.s.r.). Variation of the ligand-to-copper(II) ratio yielded solids having the following empirical formulae: [Cu(4,6DMAH)₄]X₂ (X=BF₄), [Cu(4,6DMAH)₂X₂] (X=NO₃, Cl) and [Cu(4,6DMAH)X₂] (X=Br). In addition, a deprotonated ligand complex, Cu(4,6DMA)₂, was prepared using copper(II) acetate. The Sigand usually binds to the copper(II) centresvia theN-oxide oxygen and only the deprotonated ligand coordinatesvia the exocyclic nitrogen as well as the TV-oxide oxygen. The complexes involving coordinated anions and at least two ligands are monomeric while Cu(4,6DMAH)Br₂ is polymeric. The ring substituents affect either the stoichiometry or the stereochemistry of these solids when compared to less sterically demanding 2-aminopyridineN-oxides.     

Silver(I) complexes of 2‐(2‐amino­eth­yl)pyridine: nitrate and perchlorate salts of bis­[μ‐2‐(2‐amino­eth­yl)pyridine‐κ2N:N′]disilver(I)

2‐(2‐Amino­eth­yl)pyridine (2‐aep, C₇H₁₀N₂) acts as a bridging ligand in bis­[μ‐2‐(2‐amino­eth­yl)pyridine‐κ²N:N′]disilver(I) dinitrate, [Ag₂(2‐aep)₂](NO₃)₂, and bis­[μ‐2‐(2‐amino­eth­yl)­pyridine‐κ²N:N′]disilver(I) diperchlorate, [Ag₂(2‐aep)₂](ClO₄)₂. Both salts contain the dinuclear [Ag₂(2‐aep)₂]²⁺ cation, which possesses a crystallographic inversion center. The Ag⋯Ag distance is 3.1163 (5) Å for the nitrate and 3.0923 (3) Å for the perchlorate salt, and may indicate a weak d¹⁰–d¹⁰ inter­action in each case. Essentially linear coordination of the Ag^I atom is perturbed by weak coordination to the anionic O atoms. These latter inter­actions organize the dinuclear cations into one‐dimensional polymeric chains in the crystals of the two salts.     

Cyclometallation of 2-(2-thienyl)pyridine and 2-(3-thienyl)pyridine with palladium(II), rhodium(III) and ruthenium(II)

Summary 2-(2-Thienyl)pyridine [H(2-tp)] and 2-(3-thienyl)pyridine [H(3-tp)] react with lithium tetrachloropalladate(II), hexachlorotetrakis(tri-n-butylphosphine) dirhodium(III), and tetrachlorohexacarbonyldiruthenium(II) to give [PdCl(C-N)]₂-(CN=2-tp and 3-tp), [RhCl₂(C-N)PBu₃]₂ (C-N = 2-tp and 3-tp), and [RuCl(2-tp)(CO)₂]₂, respectively. Some bromo analogues are also prepared. These complexes react with pyridine and tri-n-butylphosphine to give adducts in which 2-tp is chelated through pyridine-N and thiophene-3-C and 3-tp through pyridine-N and thiophene-2-C atoms. The structures of these complexes are similar to those of the corresponding complexes of cyclometallated 2-phenylpyridine.     

1-(2′-Pyridylazo)-2-naphtholate complexes of ruthenium: Synthesis,characterization, and DNA binding properties

Reaction of 1-(2′-pyridylazo)-2-naphthol (Hpan) with [Ru(dmso)₄Cl₂] (dmso = dimethylsulfoxide), [Ru(trpy)Cl₃] (trpy = 2,2′,2″-terpyridine), [Ru(bpy)Cl₃] (bpy = 2,2′-bipyridine) and [Ru(PPh₃)₃Cl₂] in refluxing ethanol in the presence of a base (NEt₃) affords, respectively, the [Ru(pan)₂], [Ru(trpy)(pan)]⁺ (isolated as perchlorate salt), [Ru(bpy)(pan)Cl] and [Ru(PPh₃)₂(pan)Cl] complexes. Structures of these four complexes have been determined by X-ray crystallography. In each of these complexes, the pan ligand is coordinated to the metal center as a monoanionic tridentate N,N,O-donor. Reaction of the [Ru(bpy)(pan)Cl] complex with pyridine (py) and 4-picoline (pic) in the presence of silver ion has yielded the [Ru(bpy)(pan)(py)]⁺ and [Ru(bpy)(pan)(pic)]⁺ complexes (isolated as perchlorate salts), respectively. All the complexes are diamagnetic (low-spin d⁶, S = 0) and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ru(II)–Ru(III) oxidation on the positive side of SCE. Except in the [Ru(pan)₂] complex, a second oxidative response has been observed in the other five complexes. Reductions of the coordinated ligands have also been observed on the negative side of SCE. The [Ru(trpy)(pan)]ClO₄, [Ru(bpy)(pan)(py)]ClO₄ and [Ru(bpy)(pan)(pic)]ClO₄ complexes have been observed to bind to DNA, but they have not been able to cleave super-coiled DNA on UV irradiation.     

Nickel(II) and copper(II) complexes of 2-(2-pyridyl)benzimidazole: synthesis and structural characterization

2-(2-Pyridyl)benzimidazole (PBI) was synthesized by solvent-free aldol condensation and complexed with nickel(II) and copper(II) nitrate and perchlorate salts by simple reactions at room temperature. The transition metal complexes [Ni(PBI)₂NO₃](NO₃) (1), [Ni(PBI)₃](ClO₄)₂·1.5H₂O (2), [Cu(PBI)₂NO₃](NO₃) (3), and [Cu(PBI)₃](ClO₄)₂·3H₂O (4) (PBI = 2-(2-pyridyl)benzimidazole) were synthesized in good yield and structurally characterized by X-ray crystallography, infrared absorption spectroscopy, and elemental analysis. Complexes 1 and 3 are isostructural, crystallizing in the same space group P2₁/c. Both the nickel(II) and copper(II) atoms have distorted square pyramidal geometries. The metal centers in these complexes are coordinated by two molecules of the bidentate ligand (PBI) and an O-atom of the coordinated nitrate anion. Complexes 2 and 4 are also isostructural but do not crystallize in the same space group: P-1 for 2 and Pccn for 4. The geometry around both the nickel(II) and the copper(II) centers is distorted octahedral. Here, the metal atoms are coordinated by three molecules of 2-(2-pyridyl)benzimidazole. The copper(II) complex 4 has 2-fold symmetry with one of the three PBI ligands being positionally disordered about the 2-fold axis. Intermolecular N–H···O hydrogen bonds, involving the NH H-atom and an O-atom of the coordinated nitrate anion, are observed in all four complexes. In 1 and 3, this gives rise to the formation of centrosymmetric dimer-like structures that are decorated by hydrogen-bonded nitrate anions. In 2 and 4 the perchlorate anions and the water molecules of crystallization are involved in N–H···O and O–H···O hydrogen bonds bridging two symmetry-related cations, thus forming cyclic arrangements. In the case of complex 4, this leads to the formation of two-dimensional hydrogen-bonded networks parallel to plane (011). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synergistic extraction studies of uranium(VI) and plutonium(VI) with some β-diketones and heterocyclic N-oxides

The equilibrium constants for coordination of methyl substituted pyridine N-oxides with plutonium(VI) thenoyl trifluoroacetonate in chloroform (K_s) follow an order similar to those of the analogous uranium(VI) complexes indicating steric hindrance to bonding in the case of ortho substituted pyridine N-oxides. The extraction constants (k) of Pu(VI) chelates with various β-diketones are found to be only marginally higher than the values for the corresponding uranium(VI) chelates which is in conformity with the close similarity of the ionic radii of PuO ₂ ²⁺ and UO ₂ ²⁺ .     

Synthesis and crystal structures of Cd(II) complexes with di-pyridyl hexa-azamacrocyclic ligands having cyano pendant-arms

The coordination capability of two pendant-armed azamacrocyclic ligands with cyanoethyl L¹and cyanomethyl L² pendant groups towards cadmium nitrate and perchlorate salts was achieved. All metal complexes were characterized by elemental analysis, LSI-MS, IR, conductivity measurements and ¹H NMR spectroscopy. The X-ray crystal structure of the complexes [CdL¹](NO₃)₂, [CdL¹](ClO₄)₂ · CH₃CN, and [CdL²](ClO₄)₂ · H₂O were also determined. All the complexes are mononuclear with the metal ion in a distorted octahedral environment. The pendant groups are not coordinated to the metal due the linear nature of the cyano groups; however, different interactions between nitrate ions, nitrile groups and pyridine rings from the macrocycle have been observed in the Cd(II) complexes with L¹.     

Spectral characterization and antimicrobial activity of Cu(II) and Fe(III) complexes of 2-(5-Cl/NO2-1H-benzimidazol-2-yl)-4-Br/NO2-phenols

The compounds of 2-(5-chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitrophenols (HL_X : X = 1–4) and their copper(II) nitrate and iron(III) nitrate complexes have been synthesized and characterized. The structures of the complexes were confirmed on the basis of elemental analysis, thermal gravimetric analysis, molar conductivity and magnetic moment measurements, FT-IR, mass, and UV-Vis spectroscopy techniques. The complexes show high-thermal stability with >350°C m.p. In all complexes, the ligands are bidentate via one imine nitrogen and a phenolate oxygen. Cu(II) complexes having 1 : 2 M : L ratio are classified as non-electrolytes, whereas 1 : 1 M : L ratio is observed in Fe(III) complexes except [Fe(L₃)₂(H₂O)₂](NO₃) ? 3H₂O. The antimicrobial activities of the ligands and the complexes were evaluated using the disc diffusion method in DMSO as well as minimum inhibitory concentration dilution method against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis. Antifungal activities were reported for Candida albicans. The complexes [Fe(L₃)₂(H₂O)₂](NO₃) ? 3H₂O and [Cu(L₃)₂] ? 2H₂O are more effective against S. epidermidis than ciprofloxacin.     

N16-oxides of sparteine, 2-methylsparteine and 2-phenylsparteine as ligands; spectroscopic and DFT studies of complexes with ZnX2 (X=Cl,Br)

Six new ZnX₂ (X=Cl, Br) complexes with N16-oxides of sparteine, 2-methylsparteine and 2-phenylsparteine as ligands have been synthesized and characterized by MS, IR, NMR and DFT methods. All complexes have 1 : 1 stoichiometry. Complexation with N16-oxides involves inversion of the configuration at N16, converting ring C from a boat into a chair with the oxygen engaged in coordination. All complexes investigated are of composition [(L–H)⁺(ZnX₃)^?] (where L is N-oxide). The structures of the complexes obtained have been compared with those of the monoperchlorate salts of the N-oxides.