| 1. |
- Belanger-Chabot, Guillaume, et al.
(författare)
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Ammonia-(Dinitramido)boranes: High-Energy-Density Materials.
- 2015
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 54, s. 11730-11734
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Tidskriftsartikel (refereegranskat)abstract
- Two ammonia-(dinitramido)boranes were synthesized by the reaction of dinitroamine with ammonia-borane. These compds. are the first reported examples of (dinitramido)boranes. Ammonia-mono(dinitramido)borane is a perfectly oxygen-balanced high-energy-d. material (HEDM) composed of an ammonia-BH2 fuel group and a strongly oxidizing dinitramido ligand. Although it is thermally not stable enough for practical applications, its predicted specific impulse as a solid rocket propellant would be 333 s. Its predicted performance as an explosive matches that of pentaerythtritol tetranitrate (PETN) and significantly exceeds that of trinitrotoluene (TNT). Its structure was established by X-ray crystallog. and vibrational and multinuclear NMR spectroscopy. Addnl., the over-oxidized ammoniabis(dinitramido)borane was detected by NMR spectroscopy. [on SciFinder(R)]
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| 2. |
- Belanger-Chabot, Guillaume, et al.
(författare)
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[BH3C(NO2)3]-: The First Room-Temperature Stable (Trinitromethyl)borate.
- 2013
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 52:42, s. 11002-11006
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Tidskriftsartikel (refereegranskat)abstract
- The first stable (trinitromethyl)borate anion [BH3C(NO2)3]- was synthesized and structurally characterized. The BH3 group in [BH3C(NO2)3]- provides a significant increase in stability compared to the previously studied BCl3 analog. The [Na(glyme)2]+, PNP+, and PPh4+ salts of [BH3C(NO2)3]- were successfully isolated and characterized by NMR and vibrational spectroscopy. The PNP+ salt was structurally characterized, confirming the theor. predicted B-C connectivity. [on SciFinder(R)]
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| 3. |
- Belanger-Chabot, Guillaume, et al.
(författare)
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Dinitramidoborates, a Fascinating Case of Competing Oxygen and Nitrogen Donors and Tautomerism
- 2017
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Ingår i: Angewandte Chemie. - : Wiley. - 1521-3773 .- 1433-7851. ; 56:36, s. 10881-10885
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of the BH4- anion with equimolar amounts of HN(NO2)2 or of BH3*THF with K+[N(NO2)2]- produced a mono-substituted [BH3N(NO2)2]- anion which contains a B-N connected dinitramido ligand. The reaction of BH4- with two equivalents of HN(NO2)2 afforded the di-substituted borate anion consisting of two isomers, one with both nitramido ligands attached to B through N and the other one with one ligand attached through N and the other one through O. The disubstituted dinitramidoborates are marginally stable under ambient conditions, and the isomer with two N-connected ligands was characterized by its crystal structure. A tri-substituted borate was tentatively identified by NMR in the reaction of BH4- with a large excess of HN(NO2)2. All anions are highly energetic. Theoretical calculations show that the energy differences between the B-N and B-O tautomers are small, explaining the observed ease of ligand exchange.
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| 4. |
- Christe, Karl O., et al.
(författare)
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Misconceptions on fluoronium ions and hypervalent fluorine cations
- 2017
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Ingår i: Journal of Fluorine Chemistry. - : Elsevier BV. - 0022-1139. ; 204:Supplement C, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- In a recent publication (Science, 2013, 340, 57), indirect experimental evidence was presented for the transient generation in solution of a fluorine atom symmetrically bonded to two carbon atoms. The bridging atom was described as a formally positively charged fluorine engaged in hypervalent bonding, and the molecule was referred to as a fluoronium ion. This interpretation was emphasized in chemistryworld “as the first evidence for hypervalent fluorine cations, or fluoronium ions” (chemistryworld, 4 April, 2013), in Chemical & Engineering News as “fluorine’s positive side revealed” (C & E News, 2013, 91, (14) 36), and in a Science perspective as “revealing the positive side of fluorine” (Science, 2013, 340, 41). A critical examination of these interpretations shows that this symmetrically bonded fluorine atom does not carry a positive charge and is not hypervalent or hypercoordinate. Furthermore, it is shown that, in contrast to the “fluoronium ions” which always contain partially negatively charged fluorine atoms, the iodonium cations are true halonium ions according to the IUPAC definition which requires a positive charge on the halogen atom. The calculated partial charges on the halogen atoms in chlor- onium and bromonium cations are method dependent and can vary from compound to compound, and therefore are more ambiguous.
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| 5. |
- Christe, Karl O., et al.
(författare)
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Synthesis and Characterization of Fluorodinitroamine, FN(NO2)2.
- 2014
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 54, s. 1316-1320
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Tidskriftsartikel (refereegranskat)abstract
- NF3 and N(NO2)3 are known compds., whereas the mixed fluoronitroamines, FN(NO2)2 and F2NNO2, have been unknown thus far. One of these, FN(NO2)2, has now been prepd. and characterized by multinuclear NMR and Raman spectroscopy. FN(NO2)2 is the first known example of an inorg. fluoronitroamine. It is a thermally unstable, highly energetic material formed by the fluorination of the dinitramide anion using NF4+ salts as the preferred fluorinating agent. [on SciFinder(R)]
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| 6. |
- Haiges, Ralf, et al.
(författare)
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inary Group 15 Polyazides. Structural Characterization of [Bi(N3)4]−, [Bi(N3)5]2–, [bipy·Bi(N3)5]2–, [Bi(N3)6]3–, bipy·As(N3)3, bipy·Sb(N3)3, and [(bipy)2·Bi(N3)3]2 and on the Lone Pair Activation of Valence Electrons
- 2012
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 51:2, s. 1127-1141
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Tidskriftsartikel (refereegranskat)abstract
- The binary group 15 polyazides As(N3)3, Sb(N3)3, and Bi(N3)3 were stabilized by either anion or donor−acceptor adduct formation. Crystal structures are reported for [Bi(N3)4]–, [Bi(N3)5]2–, [bipy·Bi(N3)5]2–, [Bi(N3)6]3–, bipy·As(N3)3, bipy·Sb(N3)3, and [(bipy)2·Bi(N3)3]2. The lone valence electron pair on the central atom of these pnictogen(+III) compounds can be either sterically active or inactive. The [Bi(N3)5]2– anion possesses a sterically active lone pair and a monomeric pseudo-octahedral structure with a coordination number of 6, whereas its 2,2′-bipyridine adduct exhibits a pseudo-monocapped trigonal prismatic structure with CN 7 and a sterically inactive lone pair. Because of the high oxidizing power of Bi(+V), reactions aimed at Bi(N3)5 and [Bi(N3)6]– resulted in the reduction to bismuth(+III) compounds by [N3]–. The powder X-ray diffraction pattern of Bi(N3)3 was recorded at 298 K and is distinct from that calculated for Sb(N3)3 from its single-crystal data at 223 K. The [(bipy)2·Bi(N3)3]2 adduct is dimeric and derived from two BiN8 square antiprisms sharing an edge consisting of two μ1,1-bridging N3 ligands and with bismuth having CN 8 and a sterically inactive lone pair. The novel bipy·As(N3)3 and bipy·Sb(N3)3 adducts are monomeric and isostructural and contain a sterically active lone pair on their central atom and a CN of 6. A systematic quantum chemical analysis of the structures of these polyazides suggests that the M06-2X density functional is well suited for the prediction of the steric activity of lone pairs in main-group chemistry. Furthermore, it was found that the solid-state structures can strongly differ from those of the free gas-phase species or those in solutions and that lone pairs that are sterically inactive in a chemical surrounding can become activated in the free isolated species.
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| 7. |
- Prakash, G. K. Surya, et al.
(författare)
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Long-Lived Trifluoromethanide Anion: A Key Intermediate in Nucleophilic Trifluoromethylations.
- 2014
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 53:43, s. 11575-11578
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Tidskriftsartikel (refereegranskat)abstract
- The trifluoromethanide anion is the postulated key intermediate in nucleophilic trifluoromethylation reactions. However, for more than six decades, the trifluoromethanide anion was widely believed to exist only as a short-lived transient species in the condensed phase. It has now been prepd. in bulk for the first time in THF soln. The trifluoromethanide anion with the [K(18-crown-6)]+ cation was unequivocally characterized by low-temp. 19F and 13C NMR spectroscopy. Its intermediacy in nucleophilic trifluoromethylation reactions was directly evident by its reaction chem. with various electrophilic substrates. Variable-temp. NMR spectroscopy, along with quantum mech. calcns., support the persistence of the trifluoromethanide anion. [on SciFinder(R)]
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| 8. |
- Prakash, G. K. Surya, et al.
(författare)
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On the Nature of C-H⋅⋅⋅F-C Interactions in Hindered CF3-C(sp3) Bond Rotations
- 2011
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 50:49, s. 11761-11764, S11761/1-S11761/93-
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Tidskriftsartikel (refereegranskat)abstract
- In cinchona alkaloid-based scaffolds, hindered CF3 rotations have been observed. The variation in barrier heights for the CF3 rotations is controlled by the corresponding entropic changes when the substituents are changed from an allyl to a bulky 9-methylanthracenyl group. Quantum chemical and experimental studies have shown that the noncovalent C3′[BOND]H1⋅⋅⋅F[BOND]C interactions in the studied cases possess a weak hydrogen bonding-like
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| 9. |
- Rahm, Martin, 1982, et al.
(författare)
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Nitryl Cyanide, NCNO2.
- 2014
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 53:27, s. 6893-6897
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Tidskriftsartikel (refereegranskat)abstract
- The elusive nitryl cyanide, NCNO2, has been synthesized and characterized. It was prepd. in good yield, isolated by fractional condensation, characterized by NMR and vibrational spectroscopy, and studied by theor. calcns. Nitryl cyanide holds promise as a high energy d. material (HEDM) and might also prove useful as a HEDM building block. The simplicity and inherent stability of nitryl cyanide, together with the known multitude of nitriles in interstellar space, suggest that the compd. might also be a potential candidate for observations in atm. and interstellar chem. [on SciFinder(R)]
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| 10. |
- Saal, Thomas, et al.
(författare)
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Protonation of Nitramines: Where does the Proton go
- 2017
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Ingår i: Angewandte Chemie. - : Wiley. - 1521-3773 .- 1433-7851. ; 56:32, s. 9587-9591
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Tidskriftsartikel (refereegranskat)abstract
- The reactions of nitramine, N-methyl nitramine and N,N-dimethyl nitramine with anhydrous HF and the superacids HF/MF5 (M = As, Sb) were investigated at temperatures below -40 °C. In solution, exclusive O-protonation was observed by multinuclear NMR spectroscopy. Whereas no solid product could be isolated from the neat HF solutions even at -78 °C, in the HF/MF5 systems, protonated nitramine MF6- salts were isolated for the first time as moisture-sensitive solids that decompose at temperatures above -40 °C. In the solid state, depending on the counter-ion, O-protonated or N-protonated cations can be formed, in accord with theoretical calculations which show that the energy differences between O-protonation and N-protonation are very small. The [H2N-NO2H][AsF6], [H3N-NO2][SbF6], [MeHNNO2H][SbF6], and [Me2NNO2H][SbF6] salts were characterized by their X-ray crystal structures.
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