Detection of the Elusive Triazane Molecule (N3H5) in the Gas Phase

We report the detection of triazane (N₃H₅) in the gas phase. Triazane is a higher order nitrogen hydride of ammonia (NH₃) and hydrazine (N₂H₄) of fundamental importance for the understanding of the stability of single‐bonded chains of nitrogen atoms and a potential key intermediate in hydrogen–nitrogen chemistry. The experimental results along with electronic‐structure calculations reveal that triazane presents a stable molecule with a nitrogen–nitrogen bond length that is a few picometers shorter than that of hydrazine and has a lifetime exceeding 6±2 μs at a sublimation temperature of 170 K. Triazane was synthesized through irradiation of ammonia ice with energetic electrons and was detected in the gas phase upon sublimation of the ice through soft vacuum ultraviolet (VUV) photoionization coupled with a reflectron‐time‐of‐flight mass spectrometer. Isotopic substitution experiments exploiting [D₃]‐ammonia ice confirmed the identification through the detection of its fully deuterated counterpart [D₅]‐triazane (N₃D₅).     

CRYSTALLOGRAPHIC STRUCTURE AND MAGNETIC PROPERTIES OF R_(2)Fe_(17)N_(2.4)

By a proper thermal treatment, the nitrogen atoms can enter the R2Fe17 structure. The crystallographic and intrinsic magnetic properties as well as their relationship have been studied by magnetic measurements, X-ray and neutron diffraction techniques. The neutron data indicate that the nitrogen atoms occupy the interstitial sites in the Th2Zn17-type rhom-bohedral structure. The inserting nitrogen atoms are found to dilate the cell volume, increase the Curie temperature and enhance the saturation moment by raising the difference in the electron number between the spin-up and spin-down 3d subbands of the Fe atoms. Furthermore, the nitrogen atoms have an important effect on the magnetocrystallic anisotropy, which results in an easy axis with Sm2Fe17N2.4. All these make Sm2Fe17N2.4 favorable for permanent magnet applications.     

Zur Konkurrenz von Stickstoff- und Schwefel-Donoratomen in Zinkkomplexen: [Zn(bims)2][SiF6] · 5MeOH und [ZnCl(paps)]2(Zn2Cl6) (bims = Bis(2-benzimidazolylmethyl)sulfid; paps = o,o′-(N,N′-Dipicolinyliden)diazadiphenyldisulfid)

Competition between Nitrogen and Sulfur Donor Atoms in Zinc(II) Complexes: [Zn(bims)₂][SiF₆] · 5MeOH and [ZnCl(paps)]₂(Zn₂Cl₆) (bims = bis(2-benzimidazolylmethyl)sulfide; paps = o,o′-(N,N′-dipicolinylidene)diazadiphenyl-disulfide) [Zn(bims)₂](SiF₆) · 5 MeOH ( 1 ) was synthesized by reaction of Zn(SiF₆) with the ligand bis(2-benzimidazolylmethyl)sulfide (bims). Zinc is tetrahedrally coordinated by four benzimidazole nitrogen atoms of the two ligand molecules, the sulfur atom does not coordinate. From reaction of ZnCl₂ with o,o′-(N,N′-dipicolinylidene)diazadiphenyldisulfide (paps) [ZnCl(paps)]₂(Zn₂Cl₆) ( 2 ) was obtained. Here, an octahedral coordination by four nitrogen atoms, one sulfur atom of the ligand and one chloride ion was found. Both compounds were characterized by infrared and ¹H-NMR-spectroscopy as well as by single crystal X-ray structure analysis. Space groups and structural data: 1: P1 , a = 9.904(2), b = 10.951(3), c = 19.356(2) Å, α = 91.08(2), β = 91.11(2), γ = 95.74(2)°, R1 = 0.0631; 2: P1 , a = 9.051(3), b = 11.110(3), c = 15.170(4) Å, α = 92.99(2), β = 105.93(2), γ = 107.79(2)°, R1 = 0.0585.     

Theoretical study on the mechanism of the (3)CH(2) + NO(2) reaction

The complex doublet potential energy surface of the CH(2)NO(2) system is investigated at the B3LYP/6-31G(d,p) and QCISD(T)/6-311G(d,p) (single-point) levels to explore the possible reaction mechanism of the triplet CH(2) radical with NO(2). Forty minimum isomers and 92 transition states are located. For the most relevant reaction pathways, the high-level QCISD(T)/6-311 + G(2df,2p) calculations are performed at the B3LYP/6-31G(d,p) geometries to accurately determine the energetics. It is found that the top attack of the (3)CH(2) radical at the N-atom of NO(2) first forms the branched open-chain H(2)CNO(2) a with no barrier followed by ring closure to give the three-membered ring isomer cC(H(2))ON-O b that will almost barrierlessly dissociate to product P(1) H(2)CO + NO. The lesser followed competitive channel is the 1,3-H-shift of a to isomer HCN(O)OH c, which will take subsequent cis-trans conversion and dissociation to P(2) OH + HCNO. The direct O-extrusion of a to product P(3) (3)O + H(2)CNO is even much less feasible. Because the intermediates and transition states involved in the above three channels are all lower than the reactants in energy, the title reaction is expected to be rapid, as is consistent with the measured large rate constant at room temperature. Formation of the other very low-lying dissociation products such as NH(2) + CO(2), OH + HNCO and H(2)O + NCO seems unlikely due to kinetic hindrance. Moreover, the (3)CH(2) attack at the end-O of NO(2) is a barrier-consumed process, and thus may only be of significance at very high temperatures. The reaction of the singlet CH(2) with NO(2) is also briefly discussed. Our calculated results may assist in future laboratory identification of the products of the title reaction.     

Mono- and Binuclear Copper(II) and Nickel(II) Complexes with the 3,6-Bis(picolylamino)-1,2,4,5-Tetrazine Ligand

Four new compounds of formulas [Cu(hfac)₂(L)] (1), [Ni(hfac)₂(L)] (2), [{Cu(hfac)₂}₂(µ-L)]·2CH₃OH (3) and [{Ni(hfac)₂}₂(µ-L)]·2CH₃CN (4) [Hhfac = hexafluoroacetylacetone and L = 3,6-bis(picolylamino)-1,2,4,5-tetrazine] have been prepared and their structures determined by X-ray diffraction on single crystals. Compounds 1 and 2 are isostructural mononuclear complexes where the metal ions [copper(II) (1) and nickel(II) (2)] are six-coordinated in distorted octahedral MN₂O₄ surroundings which are built by two bidentate hfac ligands plus another bidentate L molecule. This last ligand coordinates to the metal ions through the nitrogen atoms of the picolylamine fragment. Compounds 3 and 4 are centrosymmetric homodinuclear compounds where two bidentate hfac units are the bidentate capping ligands at each metal center and a bis-bidentate L molecule acts as a bridge. The values of the intramolecular metal···metal separation are 7.97 (3) and 7.82 Å (4). Static (dc) magnetic susceptibility measurements were carried out for polycrystalline samples 1–4 in the temperature range 1.9–300 K. Curie law behaviors were observed for 1 and 2, the downturn of χ_MT in the low temperature region for 2 being due to the zero-field splitting of the nickel(II) ion. Very weak [J = −0.247(2) cm⁻¹] and relatively weak intramolecular antiferromagnetic interactions [J = −4.86(2) cm⁻¹] occurred in 3 and 4, respectively (the spin Hamiltonian being defined as H = −JS₁·S₂). Simple symmetry considerations about the overlap between the magnetic orbitals across the extended bis-bidentate L bridge in 3 and 4 account for their magnetic properties.     

Spectrophotometric study on the adduct formation of nickel (II)-di(2,4-dimethylphenyl)carbazonate with heterocyclic nitrogen bases

The study of the adduct formation of Ni(II)di(2,4-dimethylphenyl)cabazonate has been undertaken by synthesising and characterising it by magnetic susceptibility, IR and 1H-NMR spectral measurements. The Ni(II) chelate forms adducts with heterocyclic nitrogen bases, spectrophotometeric method has been employed for the study of the adduct formation in a monophase chloroform. Both bidentate and unsaturated monodenate heteronuclear nitrogen bases form hexa-coordinated adducts with 1:1 stoichiomety (metal chelate, base). However, the saturated nitrogen bases form penta-coordinated adducts with 1:1 stoichiometry. The results are discussed in terms of basicity and steric factors of the bases.     

Determination of Phosphorous and Nitrogen in the Sediment of Lake ‘pamvotis’ (Greece)

Abstract

Phosphorous and nitrogen nutrients in the sediment of the lake Pamvotis were determined by standard methods of analysis. The pore water of the sediment was also analyzed for orthophosphate, ammonia and nitrate content. The results give evidence that nutrient phosphorus content of the sediment is increased at the summer periods and with nitrogen content being available during the whole year gives eutrophic behavior in the lake waters. However, the winter rains reduce the phosphorous content during the spring months. The phosphorus is introduced into the lake by agricultural runoffs and by trenches from urban areas. Several isolated events originating from activities of the inhabitants of the small island and the human activities around the lake give rise to temporary pollution of the lake waters.     

ChemInform Abstract: Study of the Linkage Isomerization (Co(NH3)5NO2)Br2 ⇌ (Co(NH3) 5ONO)Br2 in the Solid State by X-Ray Powder Diffraction.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Studies on the Configuration and Structural Stability for Subnitrosyl Fe(NO)n (n = 1—4)

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Energetic Ethylene‐ and Propylene‐Bridged Bis(nitroiminotetrazolate) Salts

High energy density materials with ethylene‐ and propylene bis(5‐nitroiminotetrazolate) as the anions are reported; all salts were fully characterized by IR, and ¹H, ¹³C, and ¹⁵N NMR spectroscopy as well as elemental analyses. In addition, the heats of formation (ΔH_f) and the detonation pressures (P) and velocities (D) were calculated.

     

Organorhenium(VII) and organomolybdenum(VI) oxides: synthesis and application in oxidation catalysis

Methyltrioxorhenium(VII) has found numerous applications in various catalytic processes. In olefin epoxidation its activity can be enhanced by the addition of aromatic Lewis base nitrogen donor ligands, e.g. pyridines and pyrazoles. Due to the comparatively weak coordination of these ligands, a significant excess has to be used. Therefore the MTO/chiral Lewis base/H₂O₂ system is not very useful for chiral epoxidations. In contrast to this, dimethyldioxomolybdenum­(VI) MoO₂(CH₃)₂ undergoes a significantly stronger interaction with Lewis bases and seems, despite its generally somewhat lower activity, a reasonable candidate for application in chiral epoxidation reactions together with an appropriate chiral Lewis base ligand. Complexes of the type MoO₂(CH₃)₂L are accessible via MoO₂X₂L (X = Cl, Br). These latter compounds are even more active in olefin epoxidation than MoO₂(CH₃)₂L. Unfortunately, however, all the Mo(VI) complexes mentioned above need t‐butyl hydroperoxide as oxidizing agent and do not show activity in the presence of H₂O₂.     

Synthesis and Crystal Structure of [Cu(acac)(Hdmpz)_3]Br.EtOH

1 INTRODUCTION Diazoles have both a pyridine-type nitrogen and a pyrrole-type nitrogen (imino group), so they can act as bifunctional groups to coordinate with many metal ions or Lewis acids giving a variety of products[1, 2]. Recently researches on the pyrazole ligand have been focused on the following three sections. (i) The first is that the ligand acts as a bridged ligand and coordinates to metal forming di- and polynuclear complexes. Such system arouses much interest mainly because o…     

氮原子与卤代甲烷反应的直接氢抽提过程研究

利用B3LYP理论研究了N(~4S)+CH_3X(X = H, F, Cl)反应体系的直接氢抽提过 程,分别得到了各反应物、产物和过渡态的优化构型和谐振频率。同时应用了6- 31G(d), 6-311+G(d,p)和6-311+ + G(2d,2p)基组,考察其大小对反应体系中各物 种构型及能量的影响。理论计算表明,随着基组的增加,反应势垒逐渐降低,反应 吸热减少。对比取代甲烷的情形,结果表明反应过程中卤素原子具有典型的诱导效 应,降低了抽提势垒。