Matthew Clark

Hydrogen bonding and cation radical formation of methyl 4‐(N,N‐dimethylamino)phenyl carbamate, DMAPCMe

The donor DMAPCMe is found by theoretical calculations and cyclic voltammetry to be a moderate electron donor (calculated adiabatic ionization potential 7.17 eV, E1/2=0.55 V vs SCE), which is intermediate between the experimental ionization energies of TMPD (6.25 eV), TTF (6.83 eV), and pyrene (7.41 eV). DMAPCMe is extensively hydrogen‐bonded in solution, as seen by the growth of a shifted N–H infrared vibration band. The paramagnetic resonance spectrum of the DMAPCMe+ radical cation matches fairly well a simulated monomer radical spectrum, but there is evidence for H‐bonded paramagnetic adducts. These same adducts reduce irreversibly at 0.37 V vs SCE in acetonitrile solution.

A computational study of the possible isomers and conformations of N-trifluoromethylformamide, CF3NHC(O)H, and N-hydroxymethylidenetrifluoromethylamine, CF3NC(H)OH

Abstract A semiempirical and ab initio study of the possible isomers and conformers of both CF3NHC(O)H and CF3NC(H)OH as well as the barriers to interconversion between them was carried out. All possible geometries were fully optimized in Cs symmetry with the mopac and gaussian programs. Both the semiempirical and ab initio calculations reproduced the experimental ordering of energies, i.e. all isomers and conformers of the formamide were found to be more stable than those of the imime. In addition, transition states between the isomers were found and the barriers to isomerization based on these calculations are in good agreement with experimental data.

Reactions of tellurium chloride pentafluoride, TeF5Cl, with nitrogen nucleophiles. Preparation and characterization of the adducts (TeF4)2·NR2Cl, where R = CH3, C2H5

Abstract Reactions of TeF 5 Cl with the nitrogen nucleophiles LiN=C(CF 3 ) 2 , [(CH 3 ) 3 Si] 2 NH, and (CH 3 ) 3 SiNR 2 , Where R = CH 3 , C 2 H 5 , result in the reduction of the tellurium to Te(IV) and chlorination of the respective nucleophile. Analogous results are obtained in the reactions of TeF 5 Cl with (CH 3 ) 3 SiCN, C 6 F 5 Li, and C 6 F 5 SLi. In the case of (CH 3 ) 3 SiNR 2 , the new adducts (TeF 4 ) 2 ·NR 2 Cl are obtained in high yield. These compounds have been identified through their infrared, 1 H, 19 F, and 125 Te NMR, and mass spectra as well as by elemental analysis.

An ab initio study of the possible isomers and conformations of N-(trifluoromethyl)fluoro methanimine, CF3NCHF

Abstract The relative energies of the four possible isomers and conformations of N -(trifluoromethyl)fluoromethanimine, CF 3 NCHF, have been studied by ab initio calculations at the STO-3G, 3-21G, 4-31G and 4-31G* levels. While the STO-3G level fails to reproduce the experimentally determined order of conformational stability, the split-valence basis sets correctly predict the E -eclipsed conformation to be the most stable. Transition state energies have also been calculated, and the barriers to isomerization are in agreement with experimental data.

Crystal and molecular structure ofS-methyl(pentafluorosulfanyl)thiocarbamate

The X-ray structure of S-methyl(pentafluorosulfanyl)thiocarbamate, SF5NHC(O)SCH3, has been determined from three-dimensional diffractometer data and refined by full-matrix least-squares techniques. The crystals are monoclinic:P21/m,a=5.008 (5),b=7.811 (2),c=9.348 (4) Å, β=99.08 (7)°, andZ=2; finalR=0.046 for 517 observed reflections. The structure comprises hydrogen-bonded (NH⋯O) chains with the component monomers in thecis, cis-conformation, i.e., the arrangement of the nonhydrogen and nonfluorine atoms is nearly planar, the SF5 group and the O are in acis position with respect to the C-NH bond, and the O and the CH3 group are in acis position with respect to the C(O)-S bond. Theoretical methods including MNDO and molecular modeling were used to study the relative stabilities of the four possible conformations of SF5NHC(O)SCH3.

Investigations into the chemistry of the pentafluorochalcogen halides

Abstract The first examples of compounds containing two pentafluorosulfanyl (SF5) groups attached to the same nitrogen were prepared only a short time ago by Waterfeld and Mews [1]. We have now found a new route to one of these materials, namely (SF5) 2NCl. The details of this reaction as well as others carried out in an attempt to prepare novel perfluorinated tertiary amines will be discussed. The results of our study of the reactions of pentafluorotellurium- and pentafluoroselenium halides with a variety of reactive nitrogen and carbon nucleophiles will also be presented.