Nitrito Group Research Articles

Fluxional chromophores of bis(di-2-pyridylamine)nitritocopper(II) cations: crystal structures and electronic properties of the complexes bis(di-2-pyridylamine)nitritocopper(II) nitrate and bis(di-2-pyridylamine)nitritocopper(II) perchlorate

The X-ray crystal structures of two cation-distortion isomers of [Cu(dpyam) 2(ONO)](NO 3) ( 1) and [Cu(dpyam) 2(ONO)](ClO 4) ( 2) complexes are reported and shown to contain an asymmetric cis-distorted CuN 4O 2 chromophore. In 1 the copper atom and the asymmetrically bonded nitrito group lie on a crystallographic C 2 axis. The nitrito group is clearly disordered about the C 2 axis giving a square pyramidal cis-distorted octahedral (4+1+1*) chromophore rather than a pseudo regular cis-distorted octahedral chromphore. In 2 a distortion of the CuN 4O 2 chromophore towards a square pyramidal (4+1+1*) geometry is also present, but with well-ordered and less asymmetric nitrito group. The polycrystalline ESR spectra of 1 and 2 are temperature independent suggesting that both complexes appear to be near the static distortion limit of the fluxional CuN 4O 2 chromophore geometry. The electronic reflectance spectra of 1 and 2 involve two bands at approximately 14 700 and 9800 cm −1 for 1, and approximately 14 970 and 10 000 cm −1 for 2 and relate to the underlying static CuN 4O 2 (4+1+1*) chromophore geometry.

Second crystal form of dinitrito(1,10-phenanthroline)copper(II)

The crystal structure of a second form of green [Cu(NO2)2(phen)], where phen is 1,10-phenanthroline (C12H8N2), containing six-coordinate copper(II) with a distorted tetragonal [CuIIN2O4] core is reported. The first form had a crystal symmetry of C2/c [Breneman et al. (1999). Acta Cryst. C55, IUC9900158], while the form reported here is Pbcn. The nitrito ligands are bonded to the central copper through both O atoms, with short Cu—O bond distances of 1.987 (3) A and longer Cu—O bond distances of 2.410 (4) A. Both nitrito groups are significantly displaced from the plane defined by the 1,10-phenanthroline and the square-planar arrangement of the ligands around the CuII atom.

X-ray crystal structure of a macrocyclic tetraamine nitrito nickel(II) complex

The compound [Ni(L)(η2-NO2)]ClO4 (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized and structurally characterized. It crystallizes in the monoclinic system, space group P21/c with a = 26.899(5), b = 8.476(2), c = 23.633(5) A, β = 115.12(13)°, V = 4878.6(17) A3, and Z = 4. Each nickel(II) ion has a six-coordinated bicapped square-pyramidal geometry with four secondary amines of the macrocycle and two oxygen atoms of the bidentate nitrito group. Electronic spectra and effective magnetic moment of the complex also exhibit a high-spin six-coordinated geometry.

Hyperfine interaction in K 2Ba[Fe(NO 2) 6

Magnetic hyperfine splitting observed in the low temperature Mössbauer spectrum of potassium barium hexanitro ferrate(II), in the absence of any external field, is attributed to the 5T 2g state of the central metal atom further split into a ground 5E g state and a first excited 5B 2g state under a distorted octahedral symmetry in contrast to the earlier prediction of 1A 1g ground state on the basis of room temperature Mössbauer spectral and other properties. The central iron atom is co-ordianted to six nitrito groups (NO 2 −), having an oxidation state of +2. The temperature dependence of Mössbauer spectra is explained on the basis of electronic relaxation among the spin-orbit coupled levels of the 5E g ground state. Various kinds of electronic relaxation mechanisms have been compared to explain the proposed mechanism. The observed temperature dependent spectra with varying internal magnetic field and line width can be explained by simple spin lattice relaxation.

Synthesis and characterization of a macrocyclic nitritotetraamine nickel(II) complex

The complex [Ni(L)(O 2N)]Cl·H 2O ( 1) (L=3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized and structurally characterized. The coordination geometry around the nickel(II) ion is a six-coordinated bicapped square-pyramidal with four nitrogen atoms of the macrocycle and two oxygen atoms of the bidentate nitrito group. Electronic spectra and redox potentials of the complex also reveal a high-spin six-coordinated geometry, which is reflected by the nature of the nitrito group.

FTIR study of the nitrogen isotopic exchange between adsorbed 15NO 2 complexes and 14NO over Cu/ZSM-5 and Co/ZSM-5

The dynamics of the nitrogen isotopic exchange between adsorption complexes of 15NO 2 and gaseous 14NO has been studied by FTIR spectroscopy for Cu/ZSM-5 and Co/ZSM-5. In Co/ZSM-5 the prevailing adsorption complex is a nitrito group ligated to CO 2+ ions, Co ONO; it exchanges its nitrogen atom spontaneously with gaseous NO. In Cu/ZSM-5 nitro groups and nitrate ions prevail that are ligated to Cu 2+ ions. The isotope exchange with gaseous NO at room temperature is initially slow, but later autocatalytic. The data suggest that in this case formation of physisorbed NO 2 is rate limiting. It rapidly transfers an oxygen atom to impinging gaseous NO. The NO 2,phys is formed over pre-calcined Cu/ZSM-5 by oxygen transfer from [Cu O Cu] 2+ ions to NO, which is also the first step in the decomposition of NO into NO 2 + N 2O, as was shown previously. Once Cu ligating 15N-nitrate ions are present inside the zeolite, they exchange their 15NO 2 moeity with either 14NO 2,phys or 14NO phys. The latter process is limited to the monodentate form, Cu O NO 2, of the nitrate, and it results in the formation of Cu ligating 14N-nitrite ions and 15NO 2,phys.

Synthesis, Characterization, and Electrochemistry of Ruthenium Porphyrins Containing a Nitrosyl Axial Ligand.

Two ruthenium nitrosyl porphyrins have been synthesized and characterized by spectroscopic and electrochemical methods. The investigated compounds are represented as [(TPP)Ru(NO)(H(2)O)]BF(4) and (TPP)Ru(NO)(ONO) where TPP is the dianion of 5,10,15,20-tetraphenylporphyrin. (TPP)Ru(NO)(ONO) crystallizes in the tetragonal space group I4, with a = 13.660(1) Å, c = 9.747(1) Å, V = 1818.7(3) Å(3), and Z = 2, 233 K. The most chemically interesting feature of the structure is that the nitrosyl and O-bound nitrito groups are located axial and trans to one another. Both complexes undergo an irreversible reduction at the metal center which is accompanied by dissociation of the axial ligand trans to NO. The addition of 1-10 equiv of pyridine to [(TPP)Ru(NO)(H(2)O)]BF(4) in CH(2)Cl(2) containing 0.1 M TBAP leads to the formation of [(TPP)Ru(NO)(py)](+), a species which is reversibly reduced at E(1/2) = -0.29 V. The electrochemical data indicate that (TPP)Ru(NO)(ONO) can also be converted to [(TPP)Ru(NO)(py)](+) in CH(2)Cl(2) solutions containing pyridine but only under specific experimental conditions. This reaction does not involve a simple displacement of the ONO(-) axial ligand from (TPP)Ru(NO)(ONO) but occurs after reduction of (TPP)Ru(NO)(ONO) to (TPP)Ru(NO)(py) followed by reoxidation to [(TPP)Ru(NO)(py)](+).

New examples of dinuclear copper complexes with ferromagnetic interactions mediated by μ-1,1 bridging azido and nitrito groups: structures and magnetic properties of [L 2(N 3) 2Cu 2] and [L 2(NO 2) 2Cu 2]·H 2O (L=7-amino-4-methyl-5-aza-3-hepten-2-onato(1−))

The reaction of L 2Cu 2OAc 2 ( L = 7amino-4-methyl-5-aza-3-hepten-2-onato(−1); OAc = acetate ion) with NaN 3 and NaNO 2 yields [L 2(N 3) 2Cu 2] ( 1) and [L 2(NO 2) 2Cu 2]·H 2O ( 2), respectively. The azido complex crystallizes in the triclinic space group P 1 with a = 8.261(1), b = 9.176(1), c = 7.915(1) A ̊ , α = 113.06(1), γ = 108.90(1)°, Z = 1 . The nitrito complex also crystallizes in the triclinic space group P 1 with a = 11.523(1), b = 11.532(1), c = 112.22(1), β = 91.33(1), γ = 92.06(1)°, Z = 2 . In both cases the structure consists of neutral dinuclear entities resulting from the pairing of two mononuclear units via single-atom bridges connecting an equatorial position of a copper centre to an axial position of the other one. The copper ions adopt a (4 + 1) square-based geometry in the azido complex while (4 + 1) and (4 + 2) environments are present in the nitrito complex. Analysis of the thermal variation of the magnetic susceptibility shows that in both complexes, the two spins are ferromagnetically coupled within the dimer while an antiferromagnetic coupling is operative between dinuclear entities. Both types of interactions are larger in the case of the azido complex ( J = 24 cm −1, J′ = 1.6 cm −1) than for the nitrito complex ( J = 8 cm −1, J′ = −0.2 cm −1).

X-ray photoelectron spectroscopy/Fourier transform infrared spectroscopy study of the interaction of YBa2Cu3Ox with CO, NO, and H2+CO

The direct interaction of YBa2Cu3Ox (x=6–7) with CO, H2+CO, and NO is studied using x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and simultaneous thermal analysis. The CO interaction results in the release of CO2 at 400–800 K, and the formation of BaCO3, as well as the reduction of Cu(II) and Y(III), at temperatures above 800 K. The interaction between YBa2Cu3Ox and H2+CO results mainly in the formation of gaseous CO2 and H2O at temperatures below 830 K. At temperatures around 830 K, Cu(II) is reduced to Cu(I). In addition to barium carbonate, the methoxy group as well as the hydroxyl group can be identified on the YBa2Cu3Ox sample. At 1170 K carbides can be found on the sample surface. The NO interaction occurs at room temperature and above, leading to the release of N2, NO2, and N2O, as well as the formation of the nitride, nitrate, nitrite (NO−2), and nitrito (–ONO) groups. The nitride and nitrate species are mainly observed between 300 and 540 K, while at 830–920 K, barium nitrite is the predominant nitrogen-containing species on the surface. An active center (OBa⧠CuO) and mechanisms for the interaction between YBa2Cu3Ox and the gases are postulated and applied to explain the high catalytic activity of YBa2Cu3Ox.

XPS/FTIR study of the interaction between nitric oxide and yttrium barium copper oxide (YBa2Cu3O7)

The combination of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and simultaneous thermal analysis (STA) studies has shown that the interaction between NO and YBa[sub 2]Cu[sub 3]O[sub 7] occurs at room temperature and above, resulting in the formation of the nitride, nitrate, nitrite (NO[sub 2][sup [minus]]), and nitrito (-ONO) groups, as well as in the release of N[sub 2], NO[sub 2], and N[sub 2]O. The nitride species are observed at temperatures between 300 and 540 K but not at higher temperatures. The nitrate ion is the predominant nitrogen-containing species at temperatures below 540 K, and its concentration decays at elevated temperatures (>820 K). The nitrito group can be found at room temperature as well as elevated temperatures. The nitrite ion is observed with relatively low concentrations at lower temperatures but becomes the predominant nitrogen-containing species at high temperatures. The maximum increase in the sample weight ([approximately]7%) as measured by thermogravimetry (TG) corresponds to a net uptake of a NO[sub 2] group (or an NO molecule plus an O atom) per unit cell of YBa[sub 2]Cu[sub 3]O[sub 7]. The NO interaction also results in the oxidation of a small portion (<24%) of the lattice Cu(II) ions and, to amore » lesser extent, the oxidation of the lattice barium atoms. At 830-920 K the surface segregation of the barium atoms is evident and is thought to be indicative of the matrix degradation due to the formation of barium nitrite. A detailed mechanism of the interaction between YBa[sub 2]Cu[sub 3]O[sub 7] and NO is postulated and applied to explain the high catalytic activity for the selective reduction of NO on YBa[sub 2]Cu[sub 3]O[sub 7].« less

Synthesis and magnetic properties of nickel(II) triazamacrocyclic complexes. Crystal structure of [Ni(Me3[12]N3)(O2N)(H2O)]-(ClO4)�2H2O

The synthesis, properties and X-ray crystal structure of [Ni(Me3[12]N3)(O2N)(H2O)](ClO4)·2H2O, in which Me3[12]N3 is 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene, are described. The Ni atom is octahedrally coordinated to three N atoms of the macrocycle, two O atoms of the nitrito group and one H2O molecule. Monomeric units are linked by hydrogen bonds through one of the water of crystallization molecules, forming a chain. Magnetic measurements between 290 and 4 K reveal slight antiferromagnetic behaviour.

Darstellung, 11B-NMR- und Schwingungsspektren der closo-Hexaborate Cs2[B6H5(ONO)] und trans-Cs2[B6H4(NO2)2] / Preparation, 11Β NMR and Vibrational Spectra of the closo-Hexaborates Cs2[B6H5(ONO)] and trans-Cs2[B6H4(NO2)2

By photochemical reaction of Cs2[B6H6] with KNO2 in aqueous alkaline solution the mononitritohydrohexaborate Cs2[B6H5(ONO)] and the dinitrohydrohexaborate trans-Cs2[B6H4(NO2)2] are formed. The pure compounds have been separated by ion exchange chromatography on diethylaminoethyl cellulose. Their structures are proved by 11B NMR spectra which show the features of substituted B6 cages with C4v and D4h point symmetry. Due to the +M effect of the nitrito group in contrast to the — M effect of the nitro substituents characteristic 11B chemical shifts of opposite sign have been observed. Furthermore, the O or N coordination is distinguishable by different vibration modes within the substituents.

Synthese de polybutadienes nitres hydroxytelecheliques par nitromercuration-demercuration—II. Etude de la demercuration et caracterisation des polybutadienes nitres

The nitration of polybutadienes involving nitromercuration by [HgCl 2-NaNO 2], leads to polymers having 20–30% of modified units. Demercuration of the chains can be achieved by two distinct processes. The elimination of mercury in the presence of a base is more selective than the reduction process involving metallic hydrides which lead to significant denitration of the chains. The nitrated polymers have been characterized from both chemical and physico-chemical aspects. The relative contents of nitro and nitrito groups depend on the conditions used for the mercuration: the solvent, the stoichiometry of reactants and the presence of phenolic compounds as additives, influence the selectivity of the reaction. Molecular weight, functionality and glass transition temperature of the nitrated materials are compared with those of the initial hydroxytelechic polybutadiene.

Preparation and properties of yttrium, lanthanum, and lanthanide 3,5-dinitrobenzoates

The condition of the formation of rare earth 3,5-dinitrobenzoates were studied and their quantitative composition and solubilities in water at 298 K determined (their solubilities are of the order of 10−4 mol dm−3). From the values of solubilities in water the solubility products were established (in the order of 10−12 mol4 dm−12). The IR and X-ray spectra for the hydrated and dehydrated complexes were recorded and studied. All complexes are crystalline compounds. The condition of thermal decomposition of the complexes was also investigated. On heating above 573 K the 3,5-dinitrobenzoates decompose explosively and undergo a melting process at the same time. Accordingly, the thermal decomposition for the complexes was studied in the temperature range 273–573 K. The thermal stability data reveal them to dehydrate in two steps. From the obtained results it appears that during the dehydration process no izomerization of the nitro group to the nitrito group occurs.

Structural and spectroscopic studies of transition metal nitrite complexes. V. Crystal structures and spectra of trans-Tetrakis(pyridine)dinitritonickel(II)-pyridine (1/2), trans-Tetrakis(4-methylpyridine)dinitritonickel(II) and trans-Tetrakis(pyrazole)-dinitritonickel(II)

The crystal and molecular structures of the compounds [Ni(py)4(ONO)2],2py, [Ni(γmpy),(ONO)2] and [Ni(prz)4(ONO)2] are reported.�All three are trans nitrito complexes, the pyridine (py) compound containing two pyridine molecules of solvation. The aromatic rings in the first two complexes adopt 'paddle wheel' conformations with pitch angles varying between 40 and 70�. The nitrite ions are positioned so as to minimize repulsive interactions with the amines, and it seems likely that these groups bond through oxygen rather than nitrogen because this allows a lesser degree of interligand steric interference. The amine rings in [Ni(prz)4(ONO)2] are orthogonal to the plane containing the nickel and coordinated pyrazole nitrogen atoms; the nitrito groups are disordered between two inequivalent positions, each of which involves hydrogen bonding with the pyrazole NH groups. The nitrite infrared frequencies are similar to those observed for other nickel(II) nitrito complexes except that the antisymmetric NO stretching mode of one of the groups in the pyrazole complex is much lower in energy than expected, being in the range normally associated with a nitrogen-bonded or chelated nitrite group. It is suggested that this deviation may be caused by the hydrogen bonding in the complex. The electronic spectra of the compounds yield 10Dq values of 9100 and 8500 cm-1 for the nitrite ligands in [Ni(py)4(ONO)2] and Ni(prz)4(ONO)2], respectively, placing the nitrito group towards the weaker end of the spectro-chemical series.

Structural and spectroscopic studies of transition metal nitrite complexes. VI. Crystal structures and spectra of Hexakis(imidazole)nickel(II) dinitrate, trans-Tetrakis(2-methylimidazole)dinitritonickel(II) and cis-Tetrakis(2-methylimidazole)-(nitrito-O,O')nickel(II) nitrate-methanol (2/1)

The crystal structures and spectroscopic properties of the complexes cis-tetrakis(2-methy1imidazole)-(nitrito-O,O')nickel(II) nitrate-methanol (2/1) and trans-tetrakis(2-methylimidazole)dinitritonickel(II) are reported. The nitrite group in the former compound chelates, giving a distorted octahedral ligand coordination geometry. The ligand stereochemistry in the second complex is also a distorted octahedron, with both anions coordinating as trans nitrito groups though with significantly different Ni-O bond lengths and the nickel(II) ion being raised out of the plane of the four imidazole ligand nitrogen atoms towards the closer nitrite group. The Ni-O bond directions also deviate substantially from the fourfold symmetry axis in this latter complex. These distortions apparently occur in order to minimize ligand-ligand repulsions, particularly those associated with the amine methyl substituents. The electronic spectra of both complexes show significant band splittings due to the departure of the ligand field from regular octahedral symmetry and these are discussed in terms of the relative field strengths of the imidazole and nitrito ligands. The structure of hexakis(imidazole)nickel(II) nitrate (redetermination) is also reported.

Complex nickel nitrites. I. Complexes of N-substituted Propane-1,3-diamines

Complex nickel(II) nitrites, NiLn(NO2)2, can be prepared in good yield by the reaction of amines with K4Ni(NO2)6. Bonding of the NO2 group depends on the nature of the amine. Paramagnetic, octahedral complexes of propane-1,3-diamine (pn) and some of its N-alkyl derivatives were: pn, n = 2, dinitro; N-methyl derivative, n = 2, dinitrito; N-ethyl, n = 2, dinitrito; N,N-dimethyl, n = 1, dinitrito with bidentate nitrito groups. Corresponding thiocyanate complexes were all NiL2(NCS)2. Homopiperazine gave diamagnetic, square-planar complexes, NiL22+, for all anions examined.

The properties of trirubidium pentanitronickelate(II)

The properties of Rb3[Ni(NO2)5] have been examined and are not consistent with a five-co-ordinate structure. The magnetic data are consistent with a broadly octahedral structure, and the electron spin resonance data indicate a marked distortion from a regular configuration. The electronic spectrum is consistent with a centrosymmetric structure involving both nitrogen and oxygen co-ordinating nitrite groups. The infrared spectrum is consistent with nitrogen-co-ordinated nitrite groups and either chelating or symmetric bridging nitrito groups. The results suggest the systematic name for the complex of trirubidium catena-µ-nitritotetranitronickelate(II).

The crystal structure of disodium tetranitritonitrosohydroxyruthenate(III) 2-hydrate by neutron diffraction

The crystal structure of Na 2[Ru(NO 2) 4(NO)(OH)]·2H 2O was determined by neutron diffraction. The unit cell is monoclinic, a = 12·75; b = 14·52; c = 7·37 A ̊ ; β = 121·20° . The space group is C2/ m with 4 molecules per unit cell. The ruthenium is octahedrally co-ordinated to four nitrogens of the nitrito groups arranged in a square, the nitrogen of the nitroso, and the oxygen of the hydroxyl group. The ruthenium octahedra are held together by NaO bridges involving six fold co-ordination about the two crystallographically different sodium atoms. Hydrogen bonding apparently is not important in this crystal.

Complexes derived from ( RuNO) III and Ru IV

Nitrato, nitro and nitrito groups in various diamagnetic complexes of nitrosylruthenium have been recognised chemically or spectroscopically (infra-red) in preparations derived from aqueous nitric acid or from organic solutions. In aqueous nitric acid there is a series of mononuclear species, RuNO 3 +, RuNO.NO 3 2 +, RuNO(NO 3) 2+, RuNO (NO) 3) 3 , but a binuclear structure occurs in complexes formed by reactions in organic media. An interesting example is the complex Ru 2N 6O 15 , precipitated by the interaction of RuO 4 and nitric oxide in carbon tetrachloride solution, since the chemical and physical (infra-red spectrum, magnetic moment) properties of this complex indicate bidentate nitrato groups. Ruthenium IV appears to have a coordination number of 7 or 8 in the brown aquohydroxy complexes formed in aqueous HClO 4, HF, HNO 3 by the reduction of RuO 4 with hydrogen perodixe. In > 9 M HNO 3 , this reaction, however, produces nitrato complexes, one of which is an intensely coloured (violet) Ru IV complex with E m ∼ 35.000 closely analogous to the violet Ru IV chloro complex which has been reported as a transient species.