Preparation and Structure of [Me3N(CF3)2BCCB(CF3)2NMe3]

Bis‐trimethylamine‐ethynyl‐di‐bis(trifluoromethyl)borane [Me₃N(CF₃)₂BCCB(CF₃)₂NMe₃] ( 1 ) has been prepared from trimethylamine‐ethynyl‐bis(trifluoromethyl)borane, [HCCB(CF₃)₂NMe₃], and dimethylamino‐bis(trifluoromethyl)borane, (CF₃)₂BNMe₂. The structure of 1 has been determined by x‐ray crystallography. In the solid state the molecule possesses crystallographic C_i symmetry. The acetylenic attachment to the boron atom is characterized by a short B–C bond length of 1.565(4) Å and an essentially linear B–C–C′ bond angle of 178.1(4)°.     

Conformational equilibrium and potential energy surface of 1-fluorobutane by microwave spectroscopy and Ab initio calculations

The rotational spectra of four (GT, TT, TG, and GG) of the five possible conformers of 1-fluorobutane have been assigned by combining free jet and conventional microwave spectroscopy. The geometry optimization was performed at the MP2 (full) level of theory with the 6-31G (d) and 6-311G (d, p) basis sets and by using the B3LYP (3df, 3pd) density functional method. The relative stability of the five rotamers is calculated at the QCISD (T)/6-311G (d, p) level of theory. In spite of the fact that ab initio calculations indicated the unobserved GG' conformer to be more stable than at least one of the observed conformers it was not possible to detect its rotational spectrum. GT and TG are the most and the least stable species, respectively. The rotational spectra of several vibrational satellites of the four conformers have been studied by conventional microwave spectroscopy. The overall conformational equilibrium is governed by the two-dimensional potential energy surface of the skeletal torsions MeC-CC and FC-CC, which have been evaluated by a flexible model analysis, based on the experimental values of the relative conformational and vibrational energy spacings, and on the shifts of second moments of inertia upon conformational change and vibrational excitation. The relative energy of the fifth stable conformer (GG') was determined to be 333 cm(-1) from flexible model calculations, and to be 271 cm(-1) from the most accurate ab initio calculations.     

Halogen abstraction by triphenylphosphine of perfluorodiazadichloroalkanes containing NCCl2N groups. X-ray structure analysis of perfluoro-2,3,5,6-tetrakis(dimethylamino)-pyrazine

The reaction of perfluoro-2,2-dichloroimidazolidine (I) with triphenylphosphine (III) yields the bicyclic olefin (IV) while (V) is obtained in the presence of H₂O. From the reaction of (CF₃)₂NCCl₂NCClN(CF₃)₂ with (III), only the cyclic dimer (VI) was isolated in a yield of 6 %, predominantly polymeric material being formed. The reaction pathways agree with a carbene as intermediate. (IV), (V) and (VI) were characterized by analyses, NMR, vibrational and mass spectra. A single crystal X-ray examination of (VI), space group P2₁/n, a 9.367(2), b 10.909(3), c 10.929(3) Å, β = 103.27(2)^o, Z = 2, R = 0.109, revealed a planar, regular pyrazine ring but nonplanar N atoms in the substituent, steric interactions being relieved by rotating the amino groups out of the pyrazine plane.

     

Cesium hydridotris(trifluoromethyl)borate, Cs[(CF3)3BH

Treatment of Cs[(CF3)3BNH2] with the aminating agent H2NOSO3H in aqueous solution allowed the isolation of pure Cs[(CF3)3BH], which is stable up to 300 degrees C. Due to the strong electron-withdrawing effect of the CF3 substituents, the [(CF3)3BH]- anion behaves as a very unreactive hydride. It is stable in concentrated hydrochloric acid for many days but reacts cleanly with F2, Cl2, and Br2 to the corresponding haloborates. The molecular structure was determined by single-crystal X-ray diffraction. Crystal data: orthorhombic, space group Pnma; a = 11.4296(5) A, b = 7.9510(4) A, c = 9.7268(5) A; V = 883.94(7) A(3), Z = 4; R1 = 0.0294, wR2 = 0.0818. The anions exhibit only Cs symmetry in the lattice. The natural and deuterated anions were characterized by IR, Raman, and multinuclear NMR spectroscopy; vibrational assignments were supported by DFT calculations. QTAIM charges derived from the B3LYP electron density are given for [(CF3)3BH]- and several related anions.     

A compact solution for ion beam therapy with laser accelerated protons

The recent advancements in the field of laser-driven particle acceleration have made Laser-driven Ion Beam Therapy (L-IBT) an attractive alternative to the conventional particle therapy facilities. To bring this emerging technology to clinical application, we introduce the broad energy assorted depth dose deposition model which makes efficient use of the large energy spread and high dose-per-pulse of Laser Accelerated Protons (LAP) and is capable of delivering homogeneous doses to tumors. Furthermore, as a key component of L-IBT solution, we present a compact iso-centric gantry design with 360° rotation capability and an integrated shot-to-shot energy selection system for efficient transport of LAP with large energy spread to the patient. We show that gantry size could be reduced by a factor of 2–3 compared to conventional gantry systems by utilizing pulsed air-core magnets.     

Replacement of Trimethylamine in Trimethylamine‐trispentafluoroethyl‐borane. Structures of [(C2F5)3BNMe3], [NMe4][(C2F5)3BOH], and K[(C2F5)3BCH2(CO)C6H5]

Trimethylamine‐tris(pentafluoroethyl)borane [(C₂F₅)₃BNMe₃] ( 1 ) reacts at 190 °C with water under displacement of the trimethylamine ligand to yield the hydroxy‐tris(pentafluoroethyl)borate [(C₂F₅)₃BOH]^? ( 2 ). In tributylamine 1 reacts with alkynes HC≡CR to form novel ethynyl‐tris(pentafluoroethyl)borate anions [(C₂F₅)₃BC≡CR]^? – R = C₆H₅ ( 3 ), C₆H₄CH₃ ( 4 ), Si(CH(CH₃)₂)₃ ( 5 ) – in moderate yields. Compound 3 adds water across the triple bond to form the novel anion [(C₂F₅)₃BCH₂(CO)C₆H₅]^? ( 6 ). The structures of [(C₂F₅)₃BNMe₃], [NMe₄][(C₂F₅)₃BOH] and K[(C₂F₅)₃BCH₂(CO)C₆H₅] have been determined by x‐ray crystallography.     

Halogen exchange of flouroalkyl amines synthesis of polychloro- and bromo-trialkylamines

Fluoralkylamines (CF₃)_3?nN(CHF₂)_n, n = 1 to 3, and analogous C₂F₅ derivatives exhibit a selective reactivity of the CHF₂ group towards Lewis acids like BCl₃, TiCl₄ and BBr₃, CHCl₂ and CHBr₂ groups being formed in nearly quantitative yield. Halogenated trialkylamines of the general formulae (CF₃)_3?nN(CHCl₂)_n, n = 1 to 3, and (CF₃)_3?nN(CHBr₂)_n, n = 1 and 2, were obtained for the first time and characterized by nmr, ir, Raman and mass spectra. The halogen exchange reaction proceeds via an intermediate immonium cation, but the chloro and bromoalkyl amines are non-ionic. Both (CF₃)₂NCHF₂ and (CF₃)₂NCHCl₂ undergo photochlorination to yield (CF₃)₂NCF₂Cl and (CF₃)₂NCCl₃.     

Vibrational spectra and normal coordinate analysis of CF3 compounds: Part XLVI. Synthesis,vibrational spectra,normal coordinate analysis and electron diffraction investigation of the cis isomer of hexafluoroazomethane

The hitherto unknown cis isomer of hexafluoroazomethane has been prepared by the reaction of CICN with AgF₂ under mild conditions. It isomerizes rapidly to the trans isomer when exposed to daylight, but is stable in the dark. The compound has been characterized by NMR and UV spectra. Infrared and Raman spectra have been recorded and assigned with the assistance of a normal coordinate analysis. The molecular structure of cis-CF₃NNCF₃ has been determined by gas phase electron diffraction, and a planar CNNC skeleton, d(NN) 1.229(8) Å, d(CN) 1.494(5) Å, and ∠NNC 122.1(8)° has been established. Compared with the trans isomer, the higher sterc strain due to F?F repulsions is released by a ∮.03 Å d(CN) lengthening and a 9° widening of the NNC angle.