The first structural characterization of a binary P-N molecule: the highly energetic compound P3N21.
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Biomedical subjects
Thomas M Klapötke
Publications and source records attributed to Thomas M Klapötke.
alpha- and beta-FOX-7, polymorphs of a high energy density material, studied by X-ray single crystal and powder investigations in the temperature range from 200 to 423 K.
The alpha-beta phase transition in the novel energetic material 1,1-diamino-2,2-dinitroethylene, C2H4N4O4 (FOX-7), has been studied by single-crystal X-ray investigations at five different temperatures over the 200-393 K range. In these investigations, the positions of the hydrogen atoms were experimentally determined without any geometric constraints. In addition, X-ray powder investigations using the Guinier technique have been performed to characterize the beta-phase up to 423 K. The alpha-beta phase transition at 389 K is first order, shows a discontinuous increase of the molar volume and entropy (DeltaV = 1.75 cm3/mol, X-ray investigation; DeltaS = 1.5 cal/K mol, DSC analysis), and can be classified as displacive. The hitherto unknown structure of beta-FOX-7 was solved at 393 K and showed simple structural relations to the alpha-polymorph. The characteristic bonding in wave-shaped layers is now found for beta-FOX-7 (P2(1)2(1)2(1), z = 4, a= 6.9738(7) A, b = 6.635(1) A, c = 11.648(2) A, 393 K), as well as for alpha-FOX-7 (P2(1)/n, z = 4, a = 6.9467(7) A, b = 6.6887(9) A, c = 11.350(1) A, beta = 90.143(13) degrees , 373 K). Interestingly, whereas the intramolecular C-C, C-N, N-O, and N-H bond distances remain nearly unchanged for both polymorphs over the whole temperature range from 200 to 393 K, the two nitro groups deviate strongly from the molecular plane formed by the two carbon and two amino nitrogen atoms. In alpha-FOX-7 at 373 K, the nitro groups are twisted -47 and +6 degrees with respect to the carbon-carbon bond, but in beta-FOX-7 at 393 K, these twist angles are changed to -36 and +20 degrees . Within the layers, the FOX-7 molecules show strong pi-conjugation and extensive intra- and intermolecular hydrogen bonding. In this investigation, we have been able to show that alpha- and beta-FOX-7 build up different nets of intermolecular hydrogen bonds. In alpha-FOX-7, each oxygen atom of the nitro groups is involved in two hydrogen bonds resulting in two intramolecular and six intermolecular hydrogen bonds. But in beta-FOX-7 this coordination changes, and half of the oxygen atoms build up two and the other half build up three hydrogen bonds leading to two intramolecular and eight intermolecular hydrogen bonds. The average intermolecular hydrogen bond distance increases slightly from 2.31 A in alpha-FOX-7 to 2.52 A in beta-FOX-7. The C-NO2 bonds are of particular interest because they are referred to as the detonation trigger. It has been suggested that these bonds could be strengthened by the extensive intermolecular hydrogen bonding within the layers in both polymorphs. Such bond strengthening via cooperative effects was proposed in earlier DFT calculations on FOX-7 and may be one key to understanding its low sensitivity and high activation energy to impact.
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N-nitroso- and N-nitraminotetrazoles.
N-Nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) were synthesized from the corresponding aminotetrazoles (3a-c) either by the direct nitration with acetic anhydride/HNO3 or by dehydration of the corresponding nitrates (4a-c) with concentrated sulfuric acid. The conversion of the N-nitrosoaminotetrazoles (5a,c) with peroxytrifluoroacetic acid (CF3CO3H) yielded the corresponding nitramines in high yield (6a (82%), 6c (80%)). The N-nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) have been fully characterized by vibrational (IR, Raman) and multinuclear NMR spectroscopy (14N/15N, 1H, 13C), mass spectrometry, and elemental analysis. A detailed discussion of the 15N chemical shifts and 1H-15N coupling constants is given. The molecular structures in the solid state were determined by single-crystal X-ray diffraction (3a,c; 5a,c; 6a-c) and a detailed discussion of the molecular structures will be presented. Furthermore, the structure and bonding as well as N,N rotational barriers are discussed on the basis of theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). In the case of two N-nitraminotetrazoles (6a,c) the physicochemical properties (e.g., D, P, delta(f)H degrees) were evaluated. The heat of formation was calculated to be positive for 6a and 6c (+2.8 and +85.2 kcal mol(-1), respectively) and the calculated detonation velocity with 5988 (6a) and 7181 (6c) m s(-1) reaches values of TNT and nitroglycerin.
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Highly sensitive ammonium tetraazidoaurates(III).
The preparation and characterization of selected ammonium and methylammonium tetraazidoaurates(III) are reported. All ammonium salts were shown to be highly explosive materials. The first crystal structure of such an ammonium salt, that of [Me(4)N][Au(N(3))(4)], features polymeric units of the anion, which are linked by weak Au...Au interactions.
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The application of infrared spectroscopy to probe the surface morphology of alumina-supported palladium catalysts.
Five alumina-supported palladium catalysts have been prepared from a range of precursor compounds [palladium(II) nitrate, palladium(II) chloride, palladium(II) acetylacetonate, and tetraamminepalladium(II) tetraazidopalladate(II)] and at different metal loadings (1-7.3 wt %). Collectively, this series of catalysts provides a range of metal particle sizes (1.2-8.5 nm) that emphasize different morphological aspects of the palladium crystallites. The infrared spectra of chemisorbed CO applied under pulse-flow conditions reveal distinct groupings between metal crystallites dominated by low index planes and those that feature predominantly corner/edge atoms. Temperature-programmed infrared spectroscopy establishes that the linear CO band can be resolved into contributions from corner atoms and a combination of (111)(111) and (111)(100) particle edges. Propene hydrogenation has been used as a preliminary assessment of catalytic performance for the 1 wt % loaded catalysts, with the relative inactivity of the catalyst prepared from palladium(II) chloride attributed to a diminished hydrogen supply due to decoration of edge sites by chlorine originating from the preparative process. It is anticipated that refinements linking the vibrational spectrum of a probe molecule with surface structure and accessible adsorption sites for such a versatile catalytic substrate provide a platform against which structure/reactivity relationships can be usefully developed.
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BTA copper complexes.
Cupric oxide is one of the most important additives used (a) to catalyze decomposition reactions in gas generators to obtain cooler reaction gases, (b) as burning enhancer for ammonium perchlorate-based composite propellants, and (c) as coloring agent in pyrotechnics. In this context, the reaction of Cu(2+) ions in aqueous ammonia solution with bis(tetrazolyl)amine (H(2)bta) was investigated. Depending on the reaction conditions three complexes were obtained: Cu(bta)(NH(3))(2) (1), Cu(bta)(NH(3))(2).H(2)O (2), and (NH(4))(2)Cu(bta)(2).2.5H(2)O (3). The crystal structures of 1 and 2 are discussed with respect to the coordination mode of the dianion of N,N-bis(1(2)H-tetrazol-5-yl)-amine (bta), which mediates in the case of 1 and 2 weak superexchange interactions between the adjacent magnetic transition-metal Cu(II) cations. These antiferromagnetic interactions result from 1D copper chains over an hidden azide end-to-end bridge. Interestingly, the structural arrangement of 1 completely changes in the presence of crystal-bound water. Moreover, some physicochemical properties (e.g., heat of formation, friction, and impact sensitivity, DSC) of these complexes with respect to high-energetic materials are discussed.
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3,5-Dimethyl-1,3,5-oxadiazane-2,4,6-trione: short intermolecular contacts determining the crystal packing.
In the title compound, C5H6N2O4, the molecules lie across a crystallographic mirror plane. The compound lacks traditional hydrogen-bond donors, and hence crystals are held together by unusual C=O...O, O...C and weak C-H...O interactions, forming layers. Adjacent layers are arranged in an antiparallel manner, yielding an ABA layer sequence. The intermolecular contacts are quite short; a topological analysis of charge density based on density-functional-theory calculations was used for consideration of these short contacts and indicated a strong attractive bonding closed-shell interaction between these atoms in the crystal structure.
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The dianion of 5-cyanoiminotetrazoline: C2N62-.
Several salts (alkali, Pd(NH(3))(3), and (i)PrNH(2)) of 5-cyanoiminotetrazoline (C(2)N(6)(2-), 5-cyanoiminotetrazolinediide, CIT) were investigated. A full characterization by means of X-ray, Raman, NMR techniques, mass spectrometry, and elemental analysis is presented for the (i)()PrNH(2) (4), Cs (5), and Pd(NH(3))(3) (6) salts. The CIT dianion represents a nitrogen-rich binary CN dianion, and 5 forms monoclinic crystals (a = 7.345(2) Angstroms, b = 9.505(2) Angstroms, c = 10.198(2) Angstroms, beta = 92.12(3) degrees, space group P2(1)/n, Z = 4). DSC and in situ temperature-dependent X-ray diffraction measurements of the cesium salt 5 revealed an astonishing thermal stability accompanied by a reversible phase transition from the low-temperature alpha modification to the metastable beta modification at 253 degrees C. Above the melting point (334 degrees C), the cesium salt decomposes yielding cesium azide and cesium dicyanamide, which decomposes under further heating under release of nitrogen. The reaction of Cs(2)CIT with SO(2) resulted in the surprising formation of a new cesium salt with the 5-cyaniminotetrazoline-1-sulfonate dianion (Cs(2)CITSO(3).SO(2) (7)). 7 crystallizes in the monoclinic space group P2(1) with one SO(2) solvent molecule (a = 8.0080(2) Angstroms, b = 8.0183(2) Angstroms, c = 9.8986(3) Angstroms, beta = 108.619(1) degrees, Z = 2). The structure and bonding of the 10pi dianion are discussed on the basis B3LYP/aug-cc-pvTZ computations (MO, NBO), and the three-dimensional array of the cesium salts with respect to the Cs(delta) (+)-N(delta)(-) in 5 compared to the Cs(delta)(+)-N(delta)(-) and Cs(delta)(+)-O(delta)(-) in 7 is discussed. Due to the expected rich bonding modes of the CIT anions, the coordination chemistry with palladium was also studied, yielding monoclinic crystals of [Pd(CIT)(NH(3))(3)].H(2)O (6, a = 7.988(2) Angstroms, b = 8.375(2) Angstroms, c = 13.541(3) Angstroms, beta = 104.56 degrees, space group P2(1)/n, Z = 4). In the solid state, the complex is composed of dimers, showing two agostic interactions and an unusual close interplanar pi-pi stacking of the tetrazole moiety of the CIT ligand.
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Kinetic and donor stabilization of organotellurenyl iodides and azides.
The first tellurium compounds containing the extremely bulky tris(phenyldimethylsilyl)methyl (Tpsi) and 2,6-bis(2,4,6-triisopropylphenyl)phenyl (2,6-Trip(2)C(6)H(3)) moieties have been synthesized and isolated. Careful oxidation of the tellurolate TpsiTeLi (1) resulted in the formation of the crowded ditellane (TpsiTe)(2) (2), and iodination of 2 gave the alkanetellurenyl iodide TpsiTeI (3). In a similar fashion, the terphenyl-substituted ditellane (2,6-Trip(2)C(6)H(3)Te)(2) (9) and the arenetellurenyl iodide 2,6-Trip(2)C(6)H(3)TeI (10) were prepared. Reaction of the iodides TpsiTeI (3) and 2,6-Trip(2)C(6)H(3)TeI (10), as well as TripTeI, MesTeI (Trip = 2,4,6-triisopropylphenyl, Mes = 2,4,6-tri-tert-butylphenyl), and the donor-stabilized 2-Me(2)NCH(2)C(6)H(4)TeI, with AgN(3) resulted in the formation and isolation of the corresponding tellurenyl azides TpsiTeN(3) (4), TripTeN(3) (7), MesTeN(3) (8), 2,6-Trip(2)C(6)H(3)TeN(3) (11), and 2-Me(2)NCH(2)C(6)H(4)TeN(3) (12). Furthermore, the corresponding tris(ethyldimethylsilyl)methyl-containing (Tesi) tellurium compounds (TesiTe)(2), TesiTeI (5), and TesiTeN(3) (6) have been prepared but could not be isolated in pure form. The crystal structures of TpsiTeLi (1), (TpsiTe)(2) (2), TpsiTeN(3) (4), 2,6-Trip(2)C(6)H(3)TeI (10), 2,6-Trip(2)C(6)H(3)TeN(3) (11), and 2-Me(2)NCH(2)C(6)H(4)TeN(3) (12) have been determined by X-ray diffraction. Additionally, computational studies of the molecules for which experimental structural data were available were performed.
Azides↗
Stability of gaseous thallium monofluoride as TlF0, TlF+, and TlF2+.
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Derivatives of 1,5-diamino-1H-tetrazole: a new family of energetic heterocyclic-based salts.
1,5-Diamino-1H-tetrazole (2, DAT) can easily be protonated by reaction with strong mineral acids, yielding the poorly investigated 1,5-diaminotetrazolium nitrate (2a) and perchlorate (2b). A new synthesis for 2 is introduced that avoids lead azide as a hazardous byproduct. The reaction of 1,5-diamino-1H-tetrazole with iodomethane (7a) followed by the metathesis of the iodide (7a) with silver nitrate (7b), silver dinitramide (7c), or silver azide (7d) leads to a new family of heterocyclic-based salts. In all cases, stable salts were obtained and fully characterized by vibrational (IR, Raman) spectroscopy, multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, X-ray structure determination, and initial safety testing (impact and friction sensitivity). Most of the salts exhibit good thermal stabilities, and both the perchlorate (2b) and the dinitramide (7c) have melting points well below 100 degrees C, yet high decomposition onsets, defining them as new (7c), highly energetic ionic liquids. Preliminary sensitivity testing of the crystalline compounds indicates rather low impact sensitivities for all compounds, the highest being that of the perchlorate (2b) and the dinitramide (7c) with a value of 7 J. In contrast, the friction sensitivities of the perchlorate (2b, 60 N) and the dinitramide (7c, 24 N) are relatively high. The enthalpies of combustion (Delta(c)H degrees ) of 7b-d were determined experimentally using oxygen bomb calorimetry: Delta(c)H degrees (7b) = -2456 cal g(-)(1), Delta(c)H degrees (7c) = -2135 cal g(-)(1), and Delta(c)H degrees (7d) = -3594 cal g(-)(1). The standard enthalpies of formation (Delta(f)H degrees ) of 7b-d were obtained on the basis of quantum chemical computations using the G2 (G3) method: Delta(f)H degrees (7b) = 41.7 (41.2) kcal mol(-)(1), Delta(f)H degrees (7c) = 92.1 (91.1) kcal mol(-)(1), and Delta(f)H degrees (7d) = 161.6 (161.5) kcal mol(-)(1). The detonation velocities (D) and detonation pressures (P) of 2b and 7b-d were calculated using the empirical equations of Kamlet and Jacobs: D(2b) = 8383 m s(-)(1), P(2b) = 32.2 GPa; D(7b) = 7682 m s(-)(1), P(7b) = 23.4 GPa; D(7c) = 8827 m s(-)(1), P(7c) = 33.6 GPa; and D(7d) = 7405 m s(-)(1), P(7d) = 20.8 GPa. For all compounds, a structure determination by single-crystal X-ray diffraction was performed. 2a and 2b crystallize in the monoclinic space groups C2/c and P2(1)/n, respectively. The salts of 7 crystallize in the orthorhombic space groups Pna2(1) (7a, 7d) and Fdd2 (7b). The hydrogen-bonded ring motifs are discussed in the formalism of graph-set analysis of hydrogen-bond patterns and compared in the case of 2a, 2b, and 7b.
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1,5-diamino-4-methyltetrazolium dinitramide.
The highly friction-sensitive 1,5-diamino-4-methyltetrazolium dinitramide was synthesized by a metathetical reaction of the corresponding iodide and silver dinitramide. An intriguing interaction of one nitro group with the tetrazolium cation was found as a crystal structure determining feature (X-ray determination), and the chemical bond is discussed on the basis of the theory of atoms in molecules (AIM).
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Organotellurium(VI) azides and halides.
The reaction of azide with organotellurium(VI) halides Ph(5)TeBr and cis-(biphen)(2)TeF(2) (biphen = 2,2'-biphenyldiyl) resulted in the formation and isolation of Ph(5)TeN(3) (1) and cis-(biphen)(2)Te(N(3))(2) (2), which are the first tellurium(VI)-azide species. In addition to spectroscopic data, both crystal structures have been determined. Furthermore, the stability of possible Te(VI) species with higher azide contents Ph(x)()Te(N(3))(6)(-)(x)() and Me(x)()Te(N(3))(6)(-)(x)() as well as the syntheses and properties of their Ph/Me(x)()TeF(y)() precursors was investigated, including the crystal structure determination of trans-Ph(2)TeF(4) (3). Ab initio and density functional studies of all molecules regarding the structures and electronic populations were performed.
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The ionic isomegethic rule and additivity relationships: estimation of ion volumes. A route to the energetics and entropics of new, traditional, hypothetical, and counterintuitive ionic materials.
By virtue of our recently established relationships, knowledge of the formula unit volume, V(m), of a solid ionic material permits estimation of thermodynamic properties such as standard entropy, lattice potential energy, and, hence, enthalpy and Gibbs energy changes for reactions. Accordingly, development of an approach to obtain currently unavailable ion volumes can expose compounds containing these ions to thermodynamic scrutiny, such as predictions regarding stability and synthesis. The isomegethic rule, introduced in this paper, states that the formula unit volumes, V(m), of isomeric ionic salts are approximately the same; this rule then forms the basis for a powerful and successful means of predicting unknown ion volumes (as well as providing a means of validating existing volume and density data) and, thereby, providing solid state thermodynamic data. The rule is exploited to generate unknown ion and (by additivity) corresponding formula unit volumes.
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Ultrafast cold reactions in the bipropellant monomethylhydrazine/nitrogen tetroxide: CPMD simulations.
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CS2N3(-)-containing pseudohalide species: an experimental and theoretical study.
The first structural reports of anhydrous salts containing the CS2N3 moiety are presented. The new M(+)CS2N3- species (M = NH4 (1), (CH3)4N (2), Cs (3), K (4)) were characterized by vibrational spectroscopy (IR, Raman), as well as multinuclear NMR spectroscopy (1H, 13C, 14N NMR). Moreover, the solid-state structures of NH4CS2N3 (1) [orthorhombic, Pbca, a = 10.6787(1) A, b = 6.8762(1) A, c = 15.2174(2) A, V = 1117.40(2) A3, Z = 8] and (H4C)4NCS2N3 (2) [monoclinic, P2(1)/m, a = 5.9011(1) A, b = 7.3565(2) A, c = 10.9474(3) A, beta = 91.428(1) degrees, V = 475.09(2) A3, Z = 2] were determined using X-ray diffraction techniques. The covalent compound CH3CS2N3 (5) was prepared by the reaction of methyl iodide with sodium azidodithiocarbonate and was characterized by vibrational spectroscopy (IR, Raman), multinuclear NMR spectroscopy (1H, 13C, 14N), and X-ray diffraction techniques [monoclinic, P2(1)/m, a = 5.544(1) A, b = 6.4792(7) A, c = 7.629(1) A, beta = 105.53(2) degrees, V = 264.06(7) A3, Z = 2]. Furthermore, the gas-phase structure of 5 was calculated (MPW1PW91/cc-pVTZ) and found to be in very good agreement with the experimentally determined structure. Improved synthetic routes for the recently reported dipseudohalogen (CS2N3)2 and interpseudohalogen CS2N3CN (6) are described, and the calculated gas-phase structure of 6 was compared with the experimentally determined structure (X-ray). The vibrational spectra of 6 and HCS2N3 (7) are also reported. Furthermore, several plausible isomers for 7 were calculated in an attempt to rationalize the experimentally observed structure which has N-H and not S-H connectivity. The lowest energy isomer for 7 is in agreement with the experimentally observed structure, and the Brønsted acidity was calculated at the MPW1PW91/cc-pVTZ level of theory. The unknown CSe2N3- anion (8) was also investigated both theoretically and experimentally, and the structure and vibrational data for the unknown CTe2N3- anion (9) were investigated by quantum-chemical calculations using a quasi-relativistic pseudopotential for Te (ECP46MWB) and a cc-pVTZ basis set for C and N. The gas-phase structure of 9 is predicted to be that of a five-membered ring in analogy to the sulfur and selenium analogues.
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Isolation of a stable covalent selenium azide RSeN3.
The first covalent selenium azide 2-Me2NCH2C6H4SeN3 has been synthesized and fully characterized including crystal structure determination. As shown by the experimental results, the relative stability of RSeN3 highly depends on the nature of the coordinating ability of the substituent R, resulting in a heterocyclic zwitterionic structure.
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Dissociation of multiply ionized isocyanic acid through electron impact.
The dissociation of singly to triply ionized isocyanic acid (HNCO) has been investigated by two- and three-dimensional covariance mapping techniques through electron impact ionization at an electron energy of 200 eV. The absolute cross sections for the various dissociation channels of up to triply ionized HNCO have been measured. The HNCO dications dissociate mostly into ion pairs, while the HNCO trications dissociate mostly into ion triples, both through all the possible bond cleavages and charge allocations. Some major ion-pair dissociation channels of HNCO2+ are supposed to be sequential dissociation through initial charge separation. The metastable decay traces caused by HNCO(2+)-->H(+)+NCO+ and HNCO(+)-->HCO(+)+N have been observed on the covariance map.
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