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Karl O Christe

Publications and source records attributed to Karl O Christe.

26 records · Page 2Linked to original sources
PubMed2003

Polynitrogen chemistry: preparation and characterization of (N5)2SnF6, N5SnF5, and N5B(CF3)4.

Metathetical processes were used to convert N5SbF6 into N5[B(CF3)4] and (N5)2SnF6. The latter salt is especially noteworthy because it contains two N5+ ions per anion, thus demonstrating that salts with touching polynitrogen cations can be prepared. This constitutes an important milestone towards our ultimate goal of synthesizing a stable, ionic nitrogen allotrope. The stepwise decomposition of (N5)2SnF6 yielded N5SnF5. Multinuclear NMR spectra show that in HF the SnF5- ion exists as a mixture of Sn2F(10)(2-) and Sn4F(20)(4-) ions. Attempts to isolate FN5 from the thermolysis of (N5)2SnF6 were unsuccessful, yielding only the expected decomposition products, FN3, N2, trans-N2F2, NF3, and N2.

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PubMed2003

The (SO2)2N3- anion.

The recently proposed (SO2)2N3- anion was structurally characterized by single-crystal X-ray diffraction of the [Cs][(SO2)2N3] salt (P2(1)/c, a = 8.945(2) A, b = 10.454(2) A, c = 8.152(2) A, beta = 109.166(3) degrees, Z = 4, and R1 = 0.0329 at 130 K). In the (SO2)2N3- anion, both SO2 ligands are coordinated to one terminal nitrogen atom of the N3- anion.

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PubMed2002

Structures of the BrF(4)(+) and IF(4)(+) cations.

The large discrepancies between the calculated and observed structures for BrF(4)(+) and IF(4)(+) (Christe, K. O.; Zhang, X.; Sheehy, J. A.; Bau, R. J. Am. Chem. Soc. 2001, 123, 6338) prompted a redetermination of the crystal structures of BrF(4)(+)Sb(2)F(11)(-) (monoclinic, P2(1)/c, a = 5.2289(6) A, b = 14.510(2) A, c = 14.194(2) A, beta = 90.280(1) degrees, Z = 4) and IF(4)(+)SbF(6)(-) (orthorhombic, Ibca, a = 8.2702(9) A, b = 8.3115(9) A, c = 20.607(2) A, Z = 8). It is shown that for BrF(4)(+), the large differences were mainly due to large errors in the original experimental data. For IF(4)(+)SbF(6)(-), the geometry previously reported for IF(4)(+) was reasonably close to that found in this study despite a very large R-factor of 0.15 and a refinement in an incorrect space group. The general agreement between the calculated and the redetermined geometries of BrF(4)(+) and IF(4)(+) is excellent, except for the preferential compression of one bond angle in each ion due to the influence of interionic fluorine bridges. In BrF(4)(+), the fluorine bridges are equatorial and compress this angle. In IF(4)(+), the nature of the fluorine bridges depends on the counterion, and either the axial (in IF(4)(+)SbF(6)(-)) or the equatorial (in IF(4)(+)Sb(2)F(11)(-)) bond angle is preferentially compressed. Therefore, the geometries of the free ions are best described by the theoretical calculations.

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PubMed2002

Synthesis and characterization of the SO(2)N(3)(-), (SO(2))(2)N(3)(-), and SO(3)N(3)(-) anions.

SO(2) solutions of azide anions are bright yellow, and their Raman spectra indicate the presence of covalently bound azide. Removal of the solvent at -64 degrees C from CsN(3) or N(CH(3))(4)N(3) solutions produces yellow (SO(2))(2)N(3)(-) salts. Above -64 degrees C, these salts lose 1 mol of SO(2), resulting in white SO(2)N(3)(-) salts that are marginally stable at room temperature and thermally decompose to the corresponding azides and SO(2). These anions were characterized by vibrational and (14)N NMR spectroscopy and theoretical calculations. Slow loss of the solvent by diffusion through the walls of a sealed Teflon tube containing a sample of CsSO(2)N(3) in SO(2) resulted in white and yellowish single crystals that were identified by X-ray diffraction as CsSO(2)N(3).CsSO(3)N(3) with a = 9.542(2) A, b = 6.2189(14) A, c = 10.342(2) A, and beta = 114.958(4) degrees in the monoclinic space group P2(1)/m, Z = 2, and Cs(2)S(2)O(5).Cs(2)S(2)O(7).SO(2), respectively. Pure CsSO(3)N(3) was also prepared and characterized by vibrational spectroscopy. The S-N bond in SO(2)N(3)(-) is much weaker than that in SO(3)N(3)(-), resulting in decreased thermal stability, an increase in the S-N bond distance by 0.23 A, and an increased tendency to undergo rotational disorder. This marked difference is due to SO(3) being a much stronger Lewis acid (pF(-) value of 7.83) than SO(2) (pF(-) value of 3.99), thus forming a stronger S-N bond with the Lewis base N(3)(-). The geometry of the free gaseous SO(2)N(3)(-) anion was calculated at the RHF, MP2, B3LYP, and CCSD(T) levels. The results show that only the correlated methods correctly reproduce the experimentally observed orientation of the SO(2) group.

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