ABSTRACT
The synthesis and properties of a new class of inorganic salts, named pentafluorosulfanylnitramide salts (or pentafluorosulfanylnitraminic acid salts) [Z+SF5NNO2-], are described. A number of SF5-nitramide salts (Z+SF5NNO2-) were successfully prepared via nucleophilic displacements from carbamates and/or ion exchange techniques, but some salts [M(SF5NNO2)x; M = Li, Mg, Al] decomposed during isolation procedures and appear to be unstable in the solid state. Single-crystal X-ray diffraction was used to fully characterize the Z+SF5NNO2-, and their properties/structures are compared with those of the corresponding dinitramide salts (or dinitraminic acid salts), Z+N(NO2)2-. X-ray crystallography revealed major structural differences between N(NO2)2- and SF5N(NO2)- salts concerning the N-N distances and the angles subtended at the central nitrogen atom. In the N(NO2)2- salts, there are two nonequivalent N-N (average lengths 1.372(2) and 1.354(2) A) distances and an average N-N-N angle of 115.8(3) degrees (falls between sp3 and sp2 hybridization). In the SFsNNO2- salts, the average N-N distance is much shorter, 1.308(9) A, and the average N-N-S angle is 120.0(5) degrees (closely fits sp2 hybridization). The SF5NNO2- salts show a remarkable metrical similarity for the SF5 moiety in all structures, indicating a lack of sensitivity to its steric and electronic environment. This is in marked contrast to N(NO2)2-, where there is a wide variation in conformations adopted by these anions which can be related to their environment.
ABSTRACT
The structures of trifluoroacrylonitrile, F2C=CF-CN, monoclinic, P2(1/n) (no. 14), a = 8.595(4), b = 8.748(1), c = 5.421(1) A, beta = 102.83(2) degrees, Z = 4, and its thermally unstable isomer trifluorovinyl isocyanide, F2C=CF-NC, monoclinic, P2(1/n), a = 8.501(2), b = 8.828(2), c = 5.599(2) A, beta = 101.11(2) degrees, Z = 4 were determined by X-ray crystal structure analysis at 113 and 128 K, respectively, from single crystals grown by partial melting and gradient cooling in small glass capillaries. Selected experimental bond lengths of F2C=CF-CN/F2C=CF-NC are as follows: C=C 1.326(1)/1.304(2), C...N 1.158(1)/1.167(2) A. The C-F bond lengths of the CF2 group are significantly shorter than those of the CF(NC) and CF(CN) units, respectively. The vibrational frequencies and molecular geometries of this cyanide/isocyanide pair were also calculated by ab initio methods for comparison with the experimental results, which were found to be in general agreement.
ABSTRACT
Cytochrome cd1 from the denitrifying bacterium Pseudomonas aeruginosa catalyzes the oxygenation of carbon monoxide by dioxygen. A minimum estimate of the turnover number for this activity is 7 mol of carbon dioxide produced per hour per mole of cytochrome subunit at 30 degrees C and pH 7. The reaction is 98% inhibited by 2.5 mM cyanide, but catalase has no effect. The reaction accounts for the unusual reduction of ferric cytochrome in the presence of carbon monoxide, but no additional reducing agent. The reaction is independent of the steady-state oxidation level of the cytochrome during turnover. Under anaerobic conditions, ferricyanide plus water may substitute for dioxygen as the source of oxidizing equivalents and atomic oxygen.
