Further Insights into the Chemical Synthesis of F and on Drying moist HF.

It is well established that solid KMnF reacts with excess SbF forming elemental F. However, if the reaction is carried out in anhydrous HF (aHF) as a solvent, this is surprisingly not the case. Instead, the green Mn(IV) compound K[(MnF)(SbF)]F is obtained.

Synthesis and characterization of trifluoromethylcarboxonium salts.

The low-temperature protonation of trifluoroacetic acid with the superacids HF/SbF and HF/AsF resulted in the syntheses of the first examples of trifluoromethylcarboxonium salts. The less acidic trifluoromethylacetamide was also protonated in the same fashion, resulting in exclusive protonation of the carbonyl function. Their [SbF] and [AsF] salts were characterized by crystal structures, vibrational and multinuclear NMR spectra, and by electronic structure calculations.

Inelastic Neutron Scattering Study of Phonon Density of States of Iodine Oxides and First-Principles Calculations.

Iodine oxides IO ( = 4, 5, 6) crystallize into atypical structures that fall between molecular- and framework-base types and exhibit high reactivity in an ambient environment, a property highly desired in the so-called "agent defeat materials". Inelastic neutron scattering experiments were performed to determine the phonon density of states of the newly synthesized IO and IO samples. First-principles calculations were carried out for IO, IO, and IO to predict their thermodynamic properties and phonon density of states.

The Crucial Role of Sb F in the Chemical Synthesis of F.

The purely chemical synthesis of fluorine is a spectacular reaction which for more than a century had been believed to be impossible. In 1986, it was finally experimentally achieved, but since then this important reaction has not been further studied and its detailed mechanism had been a mystery. The known thermal stability of MnF casts serious doubts on the originally proposed hypothesis that MnF is thermodynamically unstable and decomposes spontaneously to a lower manganese fluoride and F .

Fluoro-nitrogen Cations.

The crystal structures of [NH F] [CF SO ] , [NH F ] [SbF ] , and [N F ] [Sb F ] have been determined, representing the first structural characterizations of these simple fluoro-nitrogen cations. The influences of the hybridization of the central nitrogen atom and of the number of fluorine substituents on the N-F bond lengths are evaluated for the series N F , N F , NF O , NH F , NH F , and NF . It is shown that the N-F bond length decreases from 1.

Energetic Properties, Spectroscopy, and Reactivity of NFO.

The heats of formation of NFO and similar C, S, and Si systems are predicted using the accurate composite computational chemistry Feller-Peterson-Dixon (FPD) method. The harmonic vibrational frequencies at the CCSD(T)/aug-cc-pVTZ level are reported and compared to the experimental values for NFO, its isoelectronic species CFO and NF, and NF. The infrared intensities were calculated at the MP2/aug-cc-pVTZ level and show that the infrared absorption is predicted to be like those of CFCl and SF within a factor of ∼2.

Protonation of CH N and CF N in Superacids: Isolation and Structural Characterization of Long-Lived Methyl- and Trifluoromethylamino Diazonium Ions.

The methylamino diazonium cations [CH N(H)N ] and [CF N(H)N ] were prepared as their low-temperature stable [AsF ] salts by protonation of azidomethane and azidotrifluoromethane in superacidic systems. They were characterized by NMR and Raman spectroscopy. Unequivocal proof of the protonation site was obtained by the crystal structures of both salts, confirming the formation of alkylamino diazonium ions.

Electronic Structure Predictions of the Energetic Properties of Tellurium Fluorides.

The heats of formation, bond dissociation energies (BDEs), fluoride affinities (FA), fluorocation affinities (FCA), electron affinities (EA), and ionization energies (IP) of TeF ( n = 1-6) have been predicted using the Feller-Peterson-Dixon (FPD) approach. To benchmark the approach, the bond dissociation energies of Te and TeO, the heats of formation of Te, TeH, TeO, and TeO, and the electron affinity for TeO and TeO were calculated as there are experimental thermodynamic data available for these tellurium compounds, which allow confirmation of the heat of formation of Te gas as Δ H(Te) = 50.7 ± 0.

Lewis adduct formation of hydrogen cyanide and nitriles with arsenic and antimony pentafluoride.

The reactions of hydrogen cyanide, butyronitrile, cyclopropanecarbonitrile, pivalonitrile and benzonitrile with arsenic pentafluoride and antimony pentafluoride result in the formation of 1 : 1 Lewis adducts, while malononitrile yielded both 1 : 1 and 1 : 2 Lewis adducts. All adducts were isolated and characterized by multinuclear NMR and vibrational spectroscopy, and in most cases by their X-ray crystal structures.

Synthesis and Characterization of cyclo-Pentazolate Salts of NH, NHOH, NH, C(NH), and N(CH).

A breakthrough in polynitrogen chemistry was recently achieved by our bulk synthesis of (N)(HO)(NH)Cl in which the cyclo-pentazolate anions were stabilized extensively by hydrogen bridges with the NH and OH cations. Significant efforts have been carried out to replace these nonenergetic cations and the Cl anion by more energetic cations. In this paper, the metathetical syntheses of cyclo-pentazolate salts containing the simple nitrogen-rich cations NH, NHOH, NH, C(NH), and N(CH) are reported.

Formamidinium Nitroformate: An Insensitive RDX Alternative.

Five nitroformate (trinitromethanide) salts featuring nitrogen-containing cations were prepared. The salts were characterized by multinuclear NMR, IR, and Raman spectroscopy, single-crystal X-ray analysis, differential thermal analysis, and friction and impact sensitivity testing. These experimental data are supplemented with thermochemical calculations using the Gaussian-4 composite method, and the performance of these energetic materials was calculated based on the Chapman-Jouguet thermodynamic detonation theory.

α-Fluoroalcohols: Synthesis and Characterization of Perfluorinated Methanol, Ethanol and n-Propanol, and their Oxonium Salts.

The thermally unstable, primary perfluoroalcohols, CF OH, C F OH, and nC F OH, were conveniently prepared from the corresponding carbonyl compounds in anhydrous HF solution. Experimental values for the reaction enthalpies and entropies were derived from the temperature dependence of the R COF+HF⇄R CF OH (R =F, CF , CF CF ) equilibria by NMR spectroscopy. Electronic structure calculations of the gas-phase and solution reaction energies, gas-phase acidities and heats of formation were carried out at the G3MP2 level, showing that these compounds are strong acids.

Perfluoroalcohols: The Preparation and Crystal Structures of Heptafluorocyclobutanol and Hexafluorocyclobutane-1,1-diol.

The first X-ray crystal structure of an α-fluoroalcohol is reported. Heptafluorocyclobutanol was obtained in quantitative yield from hexafluorocyclobutanone by HF addition in anhydrous hydrogen fluoride. The compound was characterized by its X-ray single crystal structure.

Synthesis of AgN and its extended 3D energetic framework.

The pentazolate anion, as a polynitrogen species, holds great promise as a high-energy density material for explosive or propulsion applications. Designing pentazole complexes that contain minimal non-energetic components is desirable in order to increase the material's energy density. Here, we report a solvent-free pentazolate complex, AgN, and a 3D energetic-framework, [Ag(NH)][Ag(N)]-, constructed from silver and cyclo-N-.

Dinitramidoborates: A Fascinating Case of Competing Oxygen and Nitrogen Donors and Tautomerism.

Reactions of the BH anion with equimolar amounts of HN(NO ) or of BH ⋅THF with K[N(NO ) ] produced a mono-substituted [BH N(NO ) ] anion, which contains a B-N connected dinitramido ligand. The reaction of BH with two equivalents of HN(NO ) 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.

Protonation of Nitramines: Where Does the Proton Go?

The reactions of nitramine, N-methyl nitramine, and N,N-dimethyl nitramine with anhydrous HF and the superacids HF/MF (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/MF systems, protonated nitramine MF salts were isolated for the first time as moisture-sensitive solids that decompose at temperatures above -40 °C.

Synthesis and Characterization of Nitro-, Trinitromethyl-, and Fluorodinitromethyl-Substituted Triazolyl- and Tetrazolyl-trihydridoborate Anions.

The problem of preparing energetic, exclusively mono-azolyl substituted hydridoborate anions in high yield and purity from [BH ] and nitroazoles by hydrogen elimination was overcome by reacting the corresponding nitroazolate anions with the BH adducts BH ⋅S(CH ) or BH ⋅THF. The highly-energetic, nitro-, trinitromethyl-, and fluorodinitromethyl- substituted triazolyl- and tetrazolyl-trihydridoborate anions were synthesized in this manner and characterized by vibrational and multinuclear NMR spectroscopy and their crystal structures. The use of excess BH resulted in some cases in the addition of a second BH molecule bound more-weakly to one of the nitrogen atoms of the azole ring.

Formation Mechanism of NF Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids.

Although the existence of the NF cation has been known for 51 years, and its formation mechanism from NF  , F  , and a strong Lewis acid in the presence of an activation energy source had been studied extensively, the mechanism had not been established. Experimental evidence had shown that the first step involves the generation of F atoms from F  , and also that the NF cation is a key intermediate. However, it was not possible to establish whether the second step involved the reaction of a F atom with either NF or the Lewis acid (LA).

Preparation and Characterization of Group 13 Cyanides.

Binary Group 13 cyanides [PPh ][Ga(CN) ], [PPh ] [In(CN) ], and [PPh ] [Tl(CN) ] were obtained in quantitative yields from the corresponding metal trifluorides MF (M=Ga, In, Tl) by fluoride-cyanide exchange reactions with Me SiCN in the presence of stoichiometric amounts of [PPh ]CN in acetonitrile solution. The 2,2'-bipyridine (bipy) adducts [(bipy) Ga(CN) ][Ga(CN) ], [(bipy)In(CN) ], and [(bipy)Tl(CN) ] were obtained from the reaction of MF with Me SiCN and bipy in acetonitrile. While the reaction of the metal trifluorides with Me SiCN in acetonitrile resulted in recovery of the starting materials, the reaction of MF with Me SiCN in pyridine (py) solution resulted in the formation of the pyridine adducts [(py) Ga(CN) ], [(py) In(CN) ], and [(py) Tl(CN) ].

The Uranium(VI) Oxoazides [UO (N ) ⋅CH CN], [(bipy) (UO ) (N ) ], [(bipy)UO (N ) ] , [UO (N ) ] , and [(UO ) (N ) ].

The reaction between [UO F ] and an excess of Me SiN in acetonitrile solution results in fluoride-azide exchange and the uranium(VI) dioxodiazide adduct [UO (N ) ⋅CH CN] was isolated in quantitative yield. The subsequent reaction of [UO (N ) ⋅CH CN] with 2,2'-bipyridine (bipy) resulted in the formation of the azido-bridged binuclear complex [(bipy) (UO ) (N ) ]. The triazido anion [(bipy)UO (N ) ] was obtained by the reaction of [UO (N ) ⋅CH CN] with stoichiometric amounts of bipy and the ionic azide [PPh ][N ].

The Binary Group 4 Azides [PPh ] [Zr(N ) ] and [PPh ] [Hf(N ) ].

The binary zirconium and hafnium polyazides [PPh ] [M(N ) ] (M=Zr, Hf) were obtained in near quantitative yields from the corresponding metal fluorides MF by fluoride-azide exchange reactions with Me SiN in the presence of two equivalents of [PPh ][N ]. The novel polyazido compounds were characterized by their vibrational spectra and their X-ray crystal structures. Both anion structures provide experimental evidence for near-linear M-N-N coordination of metal azides.

Preparation and Characterization of Antimony and Arsenic Tricyanide and Their 2,2'-Bipyridine Adducts.

The arsenic(III) and antimony(III) cyanides M(CN)3 (M=As, Sb) have been prepared in quantitative yields from the corresponding trifluorides through fluoride-cyanide exchange with Me3 SiCN in acetonitrile. When the reaction was carried out in the presence of one equivalent of 2,2'-bipyridine, the adducts [M(CN)3 ⋅(2,2'-bipy)] were obtained. The crystal structures of As(CN)3 , [As(CN)3 ⋅(2,2'-bipy)] and [Sb(CN)3 ⋅(2,2'-bipy)] were determined and are surprisingly different.

The niobium oxoazides [NbO(N3)3], [NbO(N3)3·2CH3CN], [(bipy)NbO(N3)3], Cs2[NbO(N3)5] and [PPh4]2[NbO(N3)5].

Niobium oxotriazide, [NbO(N3)3], was prepared in a fluoride-azide exchange reaction between [NbOF3] and an excess of Me3SiN3 in SO2 solution. In acetonitrile solution, the fluoride-azide exchange resulted in the isolation of the adduct [NbO(N3)3·2CH3CN]. The subsequent reaction of [NbO(N3)3] with 2,2'-bipyridine (bipy) resulted in the isolation of the bipyridine adduct [(bipy)NbO(N3)3].

Protonation of nitriles: isolation and characterization of alkyl- and arylnitrilium ions.

The reactions of acetonitrile, propionitrile, butyronitrile, N,N-dimethylaminoacetonitrile, benzonitrile, o-tolunitrile and 1,4-dicyanobenzene with HF/AsF5 or HF/SbF5 in anhydrous HF result in protonation of the nitrile. The obtained nitrilium ions were isolated as [AsF6](-), [SbF6](-) and [Sb2F11](-) salts and characterized by multinuclear NMR and vibrational spectroscopy, and their X-ray crystal structures.