Ab initio molecular orbital calculations on the associated complexes of lithium cyanide with ammonia

Ab initio molecular orbital (MO ) calculations with the 3-21G and 6-31G basis sets are carried out on a series of complexes of NH₃ with Li⁺, C?N^?, LiCN, and its isomer LiNC. The BSSE -corrected interaction energies, geometrical parameters, internal force constants, and harmonic vibrational frequencies are evaluated for 15 species. Complexes with trifurcated (C_3v) structures are calculated to be saddle points on the potential energy surfaces and have one imaginary frequency each. Calculated energies, geometrical parameters, internal force constants, and harmonic vibrational frequencies of the various species considered are discussed in terms of the nature of association of LiCN with ammonia. The vibrational frequencies of the relevant complexed species are compared with the experimental frequencies reported earlier for solutions of lithium cyanide in liquid ammonia. © 1995 John Wiley & Sons, Inc.     

Hydrogen bonded complexes and the HF vibrational energy distributions from the reaction of F atoms with NH2 and NH3

The gas phase reactions of fluorine atoms with amino radicals and ammonia molecules: F(²P)+NH₂(²B₁) → HF(¹Σ⁺)+NH(³Σ⁻) and F(²P)+NH₃(¹A₁) → HF(¹Σ⁺)+NH₂(²B₁) produce hydrogen fluoride with very different primary vibrational energy distributions as determined by low-pressure chemiluminescence studies. The reaction with NH₂ yields HF with an inverted primary vibrational energy distribution, P(v′=1:2:3:4)=0.23:0.68:0.08:0.01. The HF from the reaction with ammonia is cold (non-inverted), P(v′=1:2)=0.60:0.40. Recent experimental work on these reactions is critically assessed and some discrepancies between low-pressure chemiluminescence results and fast-flowing afterglow studies are resolved. The results of high-level ab initio calculations (up to 6–311G^** CISD) on reactants, products, and the hydrogen bonded complexes FH … NH and FH … NH₂ in the exit channels are reported. The most reliable of the computations predict that FH … NH₂ is significantly more bound than FH … NH (8.1 versus 4.1 kcal mol⁻¹ in comparison with products at the 6-311G^** MP2 level).Also, the calculated vibrational frequencies for the two hydrogen bonded complexes indicate that the FH stretch and NH₂ asymmetric stretch are much closer in frequency in FH … NH₂ than are the FH and NH stretches in FH … NH. The strong interaction and the close match of vibrational frequencies in the FH … NH₂ case both will lead to fast internal vibrational relaxation (IVR) of the reaction exoergicity from the FHN bonds, where it is released, to the NH₂ fragment in the F/NH₃ reaction. Thus, the HF produced in this reaction is expected to have less vibrational excitation than that created in the F/NH₂ reaction, for which these IVR mechanisms are not as important, and simple direct abstraction dynamics are expected.     

Theoretical Studies of Inorganic Compounds. 361) Structures and Bonding Analyses of Beryllium Chloro Complexes with Nitrogen Donors

Quantum chemical calculations at various levels of theory (BP86, B3LYP, MP2, CCSD(T), CBS‐QB3) of the beryllium complexes [BeCl₂(NHPH₃)], [BeCl₂(NHPH₃)₂], [BeCl₃(py)]^?, [BeCl₂(NH₃)], [BeCl₂(NH₃)₂], [BeCl₃(py)]^? and [BeCl₃(NH₃)]^? as well as the boron compounds [BCl₃(py)] and [BCl₃(NH₃)] show that BeCl₂ is a very strong Lewis acid. The theoretically predicted bond dissociation energy at CBS‐QB3 of Cl₂Be‐NH₃ (D_e = 32.5 kcal/mol)is even higher than that of Cl₃B‐NH₃ (D_e = 28.6 kcal/mol). Even the second ammonia molecule in [BeCl₂(NH₃)₂] still has a strong bond with D_e = 24.2 kcal/mol. The theoretically predicted bond strengths for the phosphaneimine ligands in [BeCl₂(NHPH₃)₂] are D_e = 46.7 kcal/mol for the first ligand and D_e = 29.8 kcal/mol for the second. The anion BeCl₃^? is a moderately strong Lewis acid which has bond energies of D_e = 14.1 kcal/mol in [BeCl₃(py)]^? and D_e = 14.2 kcal/mol in [BeCl₃(NH₃)]^?. The higher bond energy of [BeCl₂(NH₃)] compared with [BCl₃(NH₃)] comes from less deformation energy for BeCl₂ than for BCl₃. The intrinsic attraction between BeCl₂ and NH₃ calculated with frozen geometries of the complex geometry is ～5 kcal/mol less than the attraction between BCl₃ and NH₃. The bonding analysis with the EDA method shows that the attractive energy of the beryllium complexes comes manly from electrostatic attraction. The larger contribution of the electrostatic term is the most significant difference between the nature of the donor‐acceptor bonds of the beryllium and boron complexes.     

Tris(2‐methylphenyl)phosphonium tetrachloroborate

The title compound, C₂₁H₂₂P⁺·BCl₄^?, is the first structurally characterized example of the [HP(o‐tolyl)₃]⁺ cation, presented here with BCl₄^? as the counter‐ion. The cation has a near‐tetrahedral P atom and the BCl₄^? anion is near‐tetrahedral at boron. There are no unusually short cation–anion contacts.     

Darstellung,Kristallstruktur und spektroskopische Charakterisierung von [(H3C)3Si]NH(BCl2)

Preparation, Crystal Structure, and Spectroscopic Characterization of [(H₃C)₃Si]NH(BCl₂) [(H₃C)₃Si]NH(BCl₂) is formed during the reaction of boron trichloride with hexamethyldisilazane at low temperatures. The compound crystallizes monoclinic in space group P2₁/c with a = 953.8(2) pm, b = 1059.9(1) pm, c = 867.4(1) pm, β = 99.40(2)°; Z = 4. According to the single crystal X-ray diffraction analysis (1275 symmetry independent reflections, R = 0.040), [(H₃C)₃Si]NH(BCl₂) exists as a dimer, in the crystal. The dimers have site symmetry C_i and, within the margins of error of the structure determination, point symmetry C_2h. A characteristic feature is a planar, almost square B–N–B–N four-membered ring with the trimethylsilyl groups in trans position. The compound has been characterised by MS-, ¹H-, ¹³C-, ¹¹B-, and ²⁹Si-NMR-spectroscopy.     

Mechanochemistry of hexagonal boron nitride. 2. Reactivity upon interaction with water

Mechanical activation makes boron nitride chemically reactive with respect to water. The fact of the reaction proceeding, which is accompanied by a change in the structure of boron nitride, is confirmed by the data of IR spectroscopy, X-ray diffraction, transmission electron microscopy, differential thermal analysis, adsorption, and gravimetry. It is established that the most defective amorphous part of the material is primarily hydrolyzed. The reaction takes place at room temperature, with the conversion increasing to values of higher than 50% with the dose of mechanical energy supplied during the mechanical activation. In addition to ammonia, hydrolysis gives rise to the formation of ammonium pentaboride, NH₄B₅O₆(OH)₄ · 2H₂O. After the reaction products are removed, residual boron nitride, which is dried at T ≤ 100°C, crystallizes to form nanosized rods.     

An Efficient Synthesis of Novel Benzo‐Fused Macrocyclic Dilactams

A facile synthetic approach was adopted towards the synthesis of benzo‐fused macrocyclic lactams 2a – 2g via the base‐catalyzed condensation reaction of 2,2′‐[alkanediylbis(oxy)]bis[benzaldehydes] 3a – 3c with N,N′‐substituted bis[2‐cyanoacetamide] derivatives 7a – 7c (Scheme 2). The latter compounds were obtained by the reaction of the appropriate diamines 6a – 6c with ethyl 2‐cyanoacetate ( 4 ). Attempts to prepare the oxaaza macrocycles 2 by alternative pathways were also investigated. The novel pyrazolo‐fused macrocycles 13a and 13b were obtained in 48 and 52% yield, respectively, upon treatment of 2d and 2g with NH₂NH₂?H₂O at 100° (Scheme 4).     

BCl3-promoted synthesis of benzofurans

Lewis acidic nature of boron trichloride (BCl₃) to coordinate to the carbonyl functionality was exploited for the synthesis of benzofurans via dehydrative cyclization. This mild and efficient procedure allowed for facile access to a number of highly substituted benzofurans in a regioselective manner. The structural requirement for the successful cyclodehydration was examined in the cases, where competitive demethylation could occur.     

Phosphanimin- und Phosphaniminato-Komplexe von Bor. Synthese und Kristallstrukturen von [BF3(Me3SiNPEt3)], [BCl2(NPPh3)]2, [BCl2(NPEt3)]2, [B2Cl3(NPEt3)2]+BCl4− und [B2Cl2(NPiPr3)3]+BCl4−

Phosphaneimine and Phosphoraneiminato Complexes of Boron. Synthesis and Crystal Structures of [BF₃(Me₃SiNPEt₃)], [BCl₂(NPPh₃)]₂, [BCl₂(NPEt₃)]₂, [B₂Cl₃(NPEt₃)₂]⁺BCl₄^?, and [B₂Cl₂(NPⁱPr₃)₃]⁺BCl₄^? The title compounds have been prepared from the corresponding silylated phosphaneimines and boron trifluoride etherate and boron trichloride, respectively. The compounds form white moisture sensitive crystals, which were characterized by ¹¹B-nmr-spectroscopy, IR-spectroscopy and by crystal structure determinations. [BF₃(Me₃SiNPEt₃)] : Space group P2₁/c, Z = 4, R = 0.032 for reflections with I > 2σ(I). Lattice dimensions at ?70°C: a = 1361.0, b = 819.56, c = 1422.5 pm, β = 109.86°. The donor acceptor complex forms monomeric molecules with a B? N bond length of 157.8 pm. [BCl₂(NPPh₃)]₂ · 2 CH₂Cl₂ : Space group P2₁/c, Z = 2, R = 0.049 for reflections with I > 2σ(I). Lattice dimensions at ?50°C: a = 1184.6, b = 2086.4, c = 843.0 pm, β = 96.86°. The compound forms centrosymmetric dimeric molecules in which the boron atoms are linked to B₂N₂ four-membered rings with B? N distances of 152.7 pm via μ₂-N bridges of the NPPh₃ groups. [BCl₂(NPEt₃)]₂ : Space group Pbca, Z = 4, R = 0.029 for reflections with I > 2σ(I). Lattice dimensions at ?90°C: a = 1269.5, b = 1138.7, c = 1470.3 pm. The compound has a molecular structure corresponding to the phenyl compound with B? N ring distances of 151.0 pm. [B₂Cl₃(NPEt₃)₂]⁺BCl₄^? : Space group Pbca, Z = 8, R = 0.034 for reflections with I > 2σ(I). Lattice dimensions at ?70°C: a = 1309.3, b = 1619.8, c = 2410.7 pm. Within the cations the boron atoms are linked to planar, asymmetrical B₂N₂ four-membered rings with B? N distances of 155.1 and 143.1 pm via the μ₂-N atoms of the NPEt₃ groups. [B₂Cl₂(NPⁱPr₃)₃]⁺BCl₄^? · CH₂Cl₂: Space group Pna2, Z = 4, R = 0.033 for reflections with I > 2σ(I). Lattice dimensions at ?70°C: a = 1976.5, b = 860.2, c = 2612.7 pm. Within the cations the boron atoms are linked to planar, asymmetrical B₂N₂ four-membered rings with B? N distances of 153.7 and 150.5 pm via the μ₂-N atoms of two of the NPⁱPr₃ groups. The third NPⁱPr₃ group is terminally connected to the sp²-hybridized boron atom with a B? N distance of 133.5 pm and with a B? N? P bond angle of 165.3°.     

Die Reaktion von Phenylimino-phosphorsäure-trichlorid mit Ammoniak

Zusammenfassung Dimeres Phenylimino-phosphorsäure-trichlorid reagiert mit wasserfreiem, flüssigem NH₃ in exothermer Reaktion zu {[PhNHP(NH₂)₂]₂N}⁺Cl^–. Bei der thermischen Kondensation dieser Verbindung bei 200°/0,1 Torr entsteht unter Abspaltung von Ammoniumchlorid, Ammoniak und Anilin eine Verbindung der Zusammensetzung (PhN)_1,1P₂N₂(NH)_1,4.

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Dimeric phenylimino phosphoric acid trichloride reacts with dry liquid ammonia to {[PhNHP(NH₂)₂N]₂N}⁺Cl^–. Thermal condensation of this compound at 200°/0,1 Torr gives (PhN)_1,1P₂N₂ (NH)_1,4 under loss of ammoniumchloride, ammonia and aniline. *** DIRECT SUPPORT *** A3615112 00009

     

Deposition of boron nitride on graphite at 1300 K

A method for the deposition of BN onto graphite and other substrates is described. Boron trichloride (BCl₃) and ammonia (NH₃) diluted with Ar were used as reacting gases. The deposition process was carried out at 1300 K as well as lower temperatures in an open system at pressures of 1 atm. The consequences of the introduction of hydrogen to the system were considered. It was demonstrated that the replacement of argon with hydrogen increases the efficiency of the process as well as the theoretical rate of BN deposition. However, the acceleration of the deposition seems to be unprofitable, because the resulting supersaturation leads to the formation of an amorphous phase. The modification of the experimental conditions were proposed.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

First Characterization of an Extended Ammonium‐Ammonia Complex [{NH4(NH3)4}+(μ‐NH3)2] in the Crystal Structure of [NH4(NH3)4][Co(C2B9H11)2] · 2 NH3

The compound [NH₄(NH₃)₄][Co(C₂B₉H₁₁)₂] · 2 NH₃ ( 1 ) was prepared by the reaction of Na[Co(C₂B₉H₁₁)₂] with a proton‐charged ion‐exchange resin in liquid ammonia. The ammoniate 1 was characterized by low temperature single‐crystal X‐ray structure analysis. The anionic part of the structure consists of [Co(C₂B₉H₁₁)₂]^‐ complexes, which are connected via C‐H···H‐B dihydrogen bonds. Furthermore, 1 contains an infinite equation/tex2gif-stack-2.gif[{NH₄(NH₃)₄}⁺(μ‐NH₃)₂] cationic chain, which is formed by [NH₄(NH₃)₄]⁺ ions linked by two ammonia molecules. The N‐H···N hydrogen bonds range from 1.92 to 2.71Å (DHA = Donor···Acceptor angles: 136‐176°). Additional N‐H···H‐B dihydrogen bonds are observed (H···H: 2.3‐2.4Å).     

A simple strategy to prepare graphene oxide modified by ammonia gas catalysts for Knoevenagel condensation

A facile and simple strategy to prepare ammonia gas-modified graphene oxide (GO) catalysts was successfully established by gas–solid acid–base reaction at room temperature. The catalytic performances of ammonia gas-modified GO samples were examined in Knoevenagel condensation. The samples were characterized by X-ray diffraction, Fourier transform infra-red spectroscopy, X-ray photoelectron spectroscopy, atomic force microscope, NH₃ temperature-programmed desorption and elemental analysis. The results indicated that the excellent performances of the ammonia gas-modified GO samples in Knoevenagel condensation should be ascribed to the formation of ammonium ions (NH₄ ⁺) by the reaction between ammonia gas and the carboxyl groups located on the edge of the GO.     

Kinetics of the formation of N2O in the catalytic oxidation of NH3 on Pt-Rh filament

The kinetics of the reactions involving the formation of N₂O in the catalytic oxidation of NH₃ have been studied over polycrystalline Pt-10% Rh filament in a static system, using a Fourier transform infrared spectrometer to monitor the partial pressures of NH₃ and N₂O. The sole formation of N₂O proceeds over the filament temperatures range of 250～350°C The reaction rate is of first order in NH₃ pressure and half order in O₂ pressure, and the rate equation can be written as v = K_app· PNH₃· PO₂^1/2. The apparent activation energy of the N₂O formation reaction from the temperature coefficient of the rate constants is found to be 25 kcal/mol. The interpretation of these results in terms of Eley-Rideal type mechanism has been presented. The rate-controlling step might be the reaction between gaseous ammonia molecules and the chemisorped oxygen atoms on the surface.     

Fast atom bombardment mass spectral study of tetracycline antibiotics

In the fast atom bombardment mass spectra of tetracyclines, ammonia elimination fragment ions, [M + H – NH₃]⁺ and [M + H – NH₃ – H₂O]⁺, appeared with considerable abundances. A plausible mechanism for the loss of ammonia from [M + H]⁺ was discussed based on results by measurements on various types of tetracyclines and benzamides as the model compounds and B/E linked scanning. The results indicated that the loss of ammonia occurred in the carboxyamide moiety in the A ring and was accelerated by an ortho-hydroxy group. The same fragmentations were observed in the electrospray mass spectra of tetracyclines with a skimmer-capillary voltage differential of 150 V.     

AlCl3 · 2NH3 – eine Verbindung mit der Kristallstruktur eines Tetraammindichloroaluminium-tetrachloroaluminats – [AlCl2(NH3)4]+[AlCl4]−

ACl₃ · 2NH₃ – a Compound with the Crystal Structure of a Tetraammine Dichloroaluminiumtetrachloroaluminate – [AlCl₂(NH₃)₄]⁺[AlCl₄]^? Ammoniates of aluminiumchloride AlCl₃ · xNH₃ are in discussion as starting materials for the synthesis of aluminiumnitride. Therefore the reactions of melts of monoamminealuminiumchloride with ammonia were investigated. They react at 150°C within 10 min with one mole of ammonia to the diammoniate, [AlCl₂(NH₃)₄]⁺[AlCl₄]^?. The pure compound can be obtained by sublimation at 200°C in vacuumline apparatus. X-ray structure determination on [AlCl₂(NH₃)₄]⁺[AlCl₄]^? was carried out: see “Inhaltsübersicht”.     

On the Existence of the Trimer of Gallium Trichloride in the Gaseous Phase

The dependence of the gallium trichloride saturated and unsaturated vapor pressures on temperature was studied by the static method using a quartz membrane zero‐manometer and taking into account the volume of its working chamber and substance mass. Conclusions about the presence of a distinguishable amount of trimeric molecules along with dimeric and momomeric molecules in the vapor were drawn on the basis of the obtained data. The following rough thermodynamic characteristics of a gaseous trimer of gallium trichloride were calculated: Δ_fH° (Ga₃Cl₉, gas, 298 K) = –1466 kJ · mol^–1. S°(Ga₃Cl₉, gas, 298 K) = 654 J · mol^–1 · K^–1. These data were used to elucidate the composition of the gaseous phase at a total pressure of 1 atm in the temperature range of 400–750 K. The suggested existence of trimeric molecules was not contradicted by vibrational spectroscopic analysis of gallium trichloride saturated vapor.     

Die Kristall- und Molekularstruktur von Bordichloridazid (BCl2N3)3

Boron dichloride azide, (BCl₂N₃)₃, crystallizes in the monoclinic space group P21/c with 4 formula units per unit cell; the lattice parameters are a = 8.874, b = 14.494, c = 10.538 Å and β = 99.7°. The crystal structure was solved by direct determination of the signs of 76 structure factors and a following Fourier synthesis and was refined by the method of least squares to R = 5.8% for the 793 observed reflexions. The structure is built up from (BCl₂N₃)₃ molecules which are arranged in a way that resembles a face centered lattice. The (BN)₃ ring of the molecule has a skew boat conformation with the approximate point symmetry 2. Each boron atom is co-ordinated by two Cl and two N atoms in a distorted tetrahedral arrangement. New aspects concerning the assignment of the vibrational spectrum are discussed.     

Über die Reaktion von Phosphorpentachlorid mit den BF3-Addukten primärer Amine

Reaction of CH₃NH₂ · BF₃ and PCl₅ yields CH₃N(PCl₃)(BCl₃), (I), the behaviour of which to PCl₅, pyridine and H₂S is described. By using smaller amounts of PCl₅, CH₃N(PCl₃)(BCl₂F) (VI) is obtained. C₆H₅NH₂ · BF₃ reacts with PCl₅ to give C₆H₅N(PCl₃)(BCl₃) (IX). Physical data, especially the NMR spectra of the new compounds, are given and discussed.