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Treatment of the compound π-C5H5Fe(dmpe)I (dmpe = Me2PCH2CH2PMe2) in acetone with TlBF4 and nitrogen gas yields the binuclear dinitrogen complex {[π–C5H5Fe(dmpe)]2N2}2+(BF4–)2, 2H2O which readily reacts with carbon monoxide and LiAlH4 giving the complexes [π–C5H5Fe(dmpe)CO]+BF4– and π–C5H5Fe(dmpe)H, respectively.

Electrochemical fixation of molecular nitrogen to ammonia and hydrazine at p-type GaP photocathodes was studied in nonaqueous electrolytes containing either one of titanium tetraisopropoxide, titanium trichloride, vanadium trichloride, or chromium trichloride and a trace amount of water. Positive evidences for the nitrogen fixation were obtained in these electrolytes, but the current efficiency was quite low, and usually less than 1%. It is suggested from the present study that there are a variety of choices of electrolyte systems for the nitrogen fixation.

The evolution of hydrogen from mildly alkaline suspensions of Fe(OH)/sub 2/ appears to involve elemental iron as the intermediate, which is generated by way of a base-induced disproportionation of Fe(OH)/sub 2/. The disproportionation reaction also occurs in strongly alkaline suspensions of Fe(OH)/sub 2/; under these conditions H/sub 2/ is not formed and elemental iron accumulates in the precipitates instead. Disordered modifications of Fe(OH)/sub 2/ seem to exist which undergo disproportionation preferentially. The reactive modifications of Fe(OH)/sub 2/ are formed in higher relative concentrations or are stabilized by weak complexing or dispersing agents such as sugars and polyhydric alcohols, as well as to some extent by Mg(OH)/sub 2/ or glycine. The disproportionation of Fe(OH)/sub 2/ is significantly stimulated by ultraviolet light, as evidenced by the increased yields of H/sub 2/ in uv-light exposed samples. The evolution of H/sub 2/ is also stimulated by coprecipitation of Fe(OH)/sub 2/ with Ni(OH)/sub 2/. A variety of reducible substrates, e.g., C/sub 2/H/sub 2/, C/sub 2/H/sub 4/, CO, and N/sub 2/, act as inhibitors of H/sub 2/ formation. Reduction of these substrates occurs in a manner typical of reactions with highly dispersed elemental iron. With molecular nitrogen, hydrazine and ammonia are formed; both products were identifiedmore » by specific colorimetric tests as well as by using /sup 30/N/sub 2/-enriched nitrogen as the substrate and subsequent mass-spectrographic analysis.« less

Polymer-bound dinitrogen complexes were synthesized directly from the polymer-bound (η5-vinylmethylcyclopentadienyl)tricarbonylmanganese analogues and molecular nitrogen in tetrahydrofuran (THF)/benzene (1:5 v/v) under 3 atm of N2 at 2°C. Dinitrogen complexes were also prepared by the oxidation of the hydrazine coordinated to the polymer-bound manganese complexes with hydrogen peroxide in the presence of cupric ions. The polymer-bound dinitrogen complexes are considerably stable compared to that of the corresponding monomer model of (η5-methylcyclopentadienyl)dicarbonyldinitrogenmanganese.

Molecular nitrogen was incorporated into amides and imides by the reaction of titanium-nitrogen complex 1 [TiNMg2Cl2·THF] prepared from TiCl3 and Mg under N2 in THF with acyl chlorides 3 . The cyclic imides 10 , 12 , 14 and quinazoline 16 were obtained by the reaction of isocyanate complex[3THF·Mg2Cl2O·TiNCO] ( 6 ) generated by fixation of CO2 into titanium-nitrogen complex 1 with the corresponding cyclic acid anhydrides 9 , 11 , 13 andbenzoxazone 15 .

The thermal N2 exchange of a number of 15N-labelled diazo compounds was studied in solution. The compounds involved were 3-diazo-1-methylindolin-2-one (1), 9-diazofluorene (2), 5-diazo-1,3-cyclopentadiene-1,2,3,4-tetracarbonitrile (3), 2-diazo-2H-imidazole-4,5-dicarbonitrile (4), 4-diazocyclohexa-2,5-dienone (5), and the conjugate acids of 4 and 5, namely 4,5-dicyano-1H-imidazole-2-diazonium ion (6) and 4-hydroxybenzenediazonium ion (7). Only 1, 4, 6, and 7 exchange their diazo group with ‘external’ molecular N2. The results are explained on the hypothesis that only organic species which have an empty σ orbital and which are effective in π electron back-donation are able to react with N2. Thus, reaction with carbenes is likely to occur only if the carbene is in the 1A2 singlet state and if its electrophilicity is high.

The isomerization of 1-pentene is catalyzed by RuH2(N2)(PPh3), in toluene at 25 °C. The reaction shows two distinct stages: it proceeds very rapidly initially and is accompanied by formation of 1 mole of pentane per mole of catalyst; then the rate quickly declines and the reaction follows first order kinetics. In both stages the isomerization is retarded by the addition of N2. The kinetic data suggest that the catalytically active species are RuH2(PPh3)3 in the first stage of the isomerization and Ru(PPh3)3 in the second stage. The inhibiting effects of N2 are attributed to the ability of N2 to compete with the olefin for coordination to the metal. Infrared and NMR spectroscopic data lend support to this conclusion.

The amount of nitrogen gas, oxygen, hydrogen, and methane in soil samples from a submerged rice field was determined using the modified Koyama's apparatus and gas chromatography. Soils planted to rice had significantly larger amounts of nitrogen gas than unplanted soils. The amount of N2 in a field soil increased after transplanting and reached a maximum at tillering. The amount of N2 in unplanted submerged soils did not increase significantly during the same period.

Methanosarcina barkeri cells were observed in ammonia-free anaerobic acetate enrichments for sulfate-reducing bacteria. The capacity of Methanosarcina to grow diazotrophically was proved with a pure culture in mineral media with methanol. The cell yields with N2 or NH4+ ions as nitrogen source were 2.2 g and 6.1 g dry weight, respectively, per mol of methanol. Growth experiments with 15N2 revealed that 84% of the cell nitrogen was derived from N2. Acetylene was highly toxic to Methanosarcina and only reduced at concentrations lower than 100 μmol dissolved per 1 of medium. Assimilation of N2 and reduction of acetylene were inhibited by NH4+ ions. The experiments show that N2 fixation occurs not only in eubacteria but also in archaebacteria. The ecological significance of diazotrophic growth of Methanosarcina is discussed.

N2-fixing systems in protic media consisting of different reducing agents and molybdenum complexes (initially Mo(V)) as N2 activators form the same Mo(III) carbonyl upon replacing N2 by carbon monoxide. When CO is removed from the carbonyl, the Mo(III) complex formed becomes again capable of catalyzing the reduction of N2 to hydrazine by Ti(III) or Cr(II) hydroxide in aqueous alcohol. Sodium amalgam forms a particularly active system, reducting N2 catalytically in the presence of a Mo(III) complex already at room temperature.

The inert pyrolysis and oxidative pyrolysis of pyridine as a model nitrogen compound were investigated experimentally by means of a tubular flow reactor. The reaction temperatures were varied from 600 to 800/sup 0/C. The presence of a small amount of oxygen in a carrier gas enhanced remarkably both the decomposition rate of pyridine and the conversion rate of fuel N into N/sub 2/. Inert N/sub 2/ for fuel NO/sub x/ emission may be formed through a reaction of the type of fuel N ..-->.. NH/sub 3/ ..-->.. NH/sub 2/.... ..-->.. N/sub 2/. From the experimental results, a simple model for the conversion of fuel N into N/sub 2/ was proposed, and the applicability of the model was verified when the experimental data were satisfactorily compared with the calculated results.

1. During irradiation with light with a wavelength

Electrochemical reduction studies of dinitrogen catalyzed by Ti(OH)3−Mo(III) in an alkaline methanol solution on a mercury cathode show that the maximum yield of hydrazine (4%) and ammonia (43%) is observed at 0.5 mA/cm2 current density. In experimental conditions it corresponds to the zero-charge potential of sodium amalgam (−1.86 V).

1. Nitrogen complexes, in which the coordinated nitrogen is reduced to hydrazine under the influence of HCl, are formed when cyclohexane solutions of the phosphine hydride complexes of tungsten WH4L4, where L=PMePh2, PEtPh2, PEt2Ph, PPrPh2, PBuPh2, are irradiated in a nitrogen atmosphere. 2. Raising the nitrogen pressure from 1 to 8–16 atm increases the yield of hydrazine by 6–7 times. 3. The nature of the phosphine ligand exerts a strong effect on the yield of hydrazine. The highest yield of hydrazine is observed for the ethyl-substituted organophosphorus ligands PEtPh2 and PEt2Ph.

Etudes du processus en solution alcaline en presence d'electrodes en semiconducteurs (TiO 2 −n, GaP−n ou LuRhO 3 −n)

The reductive fixation of molecular nitrogen by glow discharge against water resulted in the formation of ammonia; amino compounds were also formed when the aqueous solution contained carboxylic acids.

Reduction of a molybdenum imide under molecular nitrogen gives ammonia and a dinitrogen complex.

A development of organometallic chemistry has revealed wide possibilities for activating various unsaturated and saturated molecules for numerous novel reactions. Many nitrogen fixating systems based on the low-valent transition metal derivatives and reducing agents have been discovered. Depending on the reaction conditions, complexed nitrogen reduction occurs to form either hydrazine derivatives or ammonia. An investigation of the nitrogen fixating systems involving Lewis acids, to regenerate the catalyst, has led to catalytic nitrogen fixation. Nitrogen activated by complex formation with transition metal compounds is capable of insertion reactions into metal—carbon bonds to form organic amines. In this connection the possibility arises of forming amines from the reaction of nitrogen with hydrocarbons in the presence of transition metal compounds. Transition metal nitrogen compounds seem to be intermediates in the 'reverse' reactions as well, i.e. decompositions of nitrogencompounds with nitrogen evolution (Sandmeyer reaction, hydrazine oxidation. etc). Unlike nitrogen, carbon dioxide is rather reactive and undergoes insertion reactions into non-transition metal-carbon boids. Carbon dioxide also appeared to be capable of direct or indirect complex formation with low-valent transition metal compounds (Ru, Rh, Pt, etc.). Investigation of the stability of such complexes permits novel synthetic and catalytic reactions to be found. Thus the formation of Me—H bonds (e.g. in the formic acid decomposition with CO2 evolution) can be utilized for catalytic reduction of olefins and other unsaturated compounds by means of formic acid. When the intermediate carbon dioxide complexes with Me—C bonds (carboxylates) are formed. the competitive reaction occurs, i.e. olefin insertion into Me—H or Me—C bonds with elimination of the respective carboxylic acid. Another interesting reaction, insertion of CO2 into Me—H or Me—C bonds, can follow either 'normal' (formation of a carbon-carbon' bond) or 'reverse' (formation of the metalloacid ester) pathways. A development of organometallic chemistry has provided unusual possibilities for activating various unsaturated and saturated molecules and introducing them into the various reactions. The present lecture deals with the problem of activation by transition 607

X-ray photoelectron Ir4f 712 -spectra of iridium(I) complexes with N 2 , CO and other ligands as well as N1s-spectra of Ir I , Co I , Fe II dinitrogen complexes and of some diazocompounds and azides were studied. Donor-acceptor properties of dinitrogen ligand, character of its coordination and electron density distribution over nitrogen atoms were investigated. Dinitrogen ligand was shown to be in overall the electron acceptor, it being more effective than Ph 3 P, CS and diphenylacetylene, close to CO and less effective than tetracyanoethylene. Dinitrogen fragment in organic diazocompounds bears the positive charge, while in transition metal complexes one of the nitrogen atoms was found to be negative charged. This results in the different reactivity of the compounds.

A new molecular nitrogen complex of iron has been prepared by the displacement of chloride ion from trans-hydridochlorodi(bisdiethylphosphinoethane)iron(II) by nitrogen in the presence of sodium tetraphenylborate.

An unstable binuclear titanium complex with molecular nitrogen has been isolated at low temperatures and its composition has been determined; the complex is an intermediate in the reduction of dinitrogen to hydrazine and ammonia.

Reaction of molecular nitrogen with sodium and naphthalene in tetrahydrofuran gives amines plus ammonia in the presence of TiCl4; a similar reaction occurs using lithium even in the absence of TiCl4.

Molecular nitrogen has been reduced to ammonia by various compounds of niobium, zirconium, and tungsten in a strongly reducing medium.

Molecular nitrogen Complexes of pentammineruthenium(II) have been prepared by reducing chloropentammineruthenium(III) in the presence of nitrous oxide.

Vacuum pyrolysis of benzo[c]cinnoline or its octachloro-derivative gives the corresponding biphenylene in high yield.

The treatment of Cp2Yb, Cp3Sm, CeCl3, Cp3Ce, and Cp3Eu·THF with excess naphthalenesodium in THF gives systems capable of reducing molecular nitrogen at 20°C and atmospheric pressure with the formation of ammonia after hydrolysis.

Summary The development of azide migration reactions is a formidable challenge because of the potential competition of side processes driven by the release of molecular nitrogen. Here, we report a conceptually novel 1,2-azide migration in an unprecedented gem-difluorination of the readily available α-vinyl azides, a transformation that enables the synthesis of a range of novel β-difluorinated alkyl azides. The practicality of the method is demonstrated by broad substrate scope, excellent functional group compatibility, and high yields. The migrating group selectivity can be tuned through electronic effects, and DFT calculations suggest 1,2-azide migration occurs via a three-membered azacyclic transition state. By using routine protocols, the β-difluorinated alkyl azide products can be easily transformed to biologically relevant β-difluorinated amines—common structural motifs in pharmaceuticals, thus demonstrating the utility of these fluorinated organic azides for pharmaceutical synthesis as well as other synthetically useful derivatives.

The Cassini mission discovered lakes and seas comprising mostly methane in the polar regions of Titan. Lakes of liquid nitrogen may have existed during the epochs of Titan’s past in which methane was photochemically depleted, leaving a nearly pure molecular nitrogen atmosphere and, thus, far colder temperatures. The modern-day small lake basins with sharp edges have been suggested to originate from dissolution processes, due to their morphological similarity to terrestrial karstic lakes. Here we analyse the morphology of the small lake basins that feature raised rims to elucidate their origin, using delay-Doppler processed altimetric and bathymetric data acquired during the last close flyby of Titan by the Cassini spacecraft. We find that the morphology of the raised-rim basins is analogous to that of explosion craters from magma–water interaction on Earth and therefore propose that these basins are from near-surface vapour explosions, rather than karstic. We calculate that the phase transition of liquid nitrogen in the near subsurface during a warming event can generate explosions sufficient to form the basins. Hence, we suggest that raised-rim basins are evidence for one or more warming events terminating a nitrogen-dominated cold episode on Titan. Some lake basins in the polar regions of Titan may be craters from nitrogen vapour explosions due to past warming, according to analysis of their morphology in comparison to terrestrial explosion craters from magma–water interaction.

Temperature and concentration measurements by Coherent Anti-Stokes Raman Scattering (CARS) of molecular nitrogen, oxygen and methane were carried out. A comparison of corrected thermocouple and CARS temperature measurements in a high-temperature furnace up to 2000 K is presented. The temperature dependent CARS spectra of N2 and O2 are evaluated by a simulation program. Agreement between CARS and thermocouple temperatures is obtained within 40 K for N2 and 80 K for O2. Good agreement is found between measurements and calculations of the decrease of CARS intensity with temperature. Various “quick-fit” methods for N2-and O2-temperature measurements from temperature sensitive spectral parameters were tested. Temperature dependent CARS spectra of thev1-fundamental of methane are recorded and the methane CARS intensity as function of temperature is measured.

In view of its abundance and availability molecular nitrogen is potentially a valuable substrate for catalytic reactions. Its present limited usage in industry is as a feedstock in the Haber-Bosch ammonia synthesis, a process requiring a heterageneous catalyst, high temperatures, and high pressures. The selective reduction of N2 to hydrazine or to organic nitrogen compounds would be highly desirable but may well be possible only with homogeneous catalysts operating under mild conditions. Thus the development of transition metal compounds capable of promoting the reduction of N2 remains a challenge to inorganic and organometallic chemists.

SummaryAerobacter aerogenes strain M5al fixing molecular nitrogen require at least 10 times more iron than do cultures using ammonium-N. Also, the organism is about 100 times more sensitive to carbon monoxide when using free than when assimilating combined nitrogen. Although there is an absolute requirement for molybdenum for nitrogen fixation by this organism, it is considerably less than that noted for many strains of the azotobacter. No specific requirement for calcium could be demonstrated.

The first step in the reduction of the dinitrogen ligand in (Cp2TiR)2N2 (R = C6H5, m-, p-CH3C6H4, C6F5, CH2C6H5) by sodium napthalene (NaC10H8) involves the removal of one Cp group per titanium atom. The resulting diimide precursor reacts with a second mole of NaC10H8 with formation of a hydrazine precursor. This compound is thermally unstable and decomposes to an ammonia precursor. A minor part of the hydrazine precursor abstracts a proton from the solvent.

The thermal N2 exchange of a number of 15N-labelled diazo compounds was studied in solution. The compounds involved were 3-diazo-1-methylindolin-2-one (1), 9-diazofluorene (2), 5-diazo-1,3-cyclopentadiene-1,2,3,4-tetracarbonitrile (3), 2-diazo-2H-imidazole-4,5-dicarbonitrile (4), 4-diazocyclohexa-2,5-dienone (5), and the conjugate acids of 4 and 5, namely 4,5-dicyano-1H-imidazole-2-diazonium ion (6) and 4-hydroxybenzenediazonium ion (7). Only 1, 4, 6, and 7 exchange their diazo group with ‘external’ molecular N2. The results are explained on the hypothesis that only organic species which have an empty σ orbital and which are effective in π electron back-donation are able to react with N2. Thus, reaction with carbenes is likely to occur only if the carbene is in the 1A2 singlet state and if its electrophilicity is high.

Photoexcitation of titanium dioxide produces reactive centers capable of reducing and possibly oxidizing chemisorbed nitrogen. Activity of the photocatalysts is significantly dependent on the source of the titanium oxide and the pretreatment conditions employed. Photocatalysts with the highest activity typically consisted of anatase containing 20–40% of rutile, obtained from iron-doped anatase by a heat-pretreatment. The photocatalytic reactions of nitrogen can occur in nature on the surface of titanium containing desert sands on exposure to sunlight and thus have ecological significance as parts of the nitrogen cycle.