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Rolf Minkwitz

Publications and source records attributed to Rolf Minkwitz.

9 recordsLinked to original sources
PubMed2002

Gas phase structure of O-nitrobis(trifluoromethyl)hydroxylamine, (CF3)2NONO2: an extremely long O-N bond.

The gas phase structure of O-nitrobis(trifluoromethyl)hydroxylamine, (CF(3))(2)NONO(2), has been determined with gas electron diffraction and quantum chemical calculations (HF, MP2, and B3LYP with 6-31G basis sets). The calculations predict a structure with C(s) overall symmetry, a planar NONO(2) skeleton, and the NO(2) group oriented anti with respect to the CNC plane. The electron diffraction intensities are reproduced very well with such a model. The molecule possesses pyramidal configuration at the amino nitrogen atom, and the following geometric parameters (r(a) values with 3sigma uncertainties) were obtained for the NONO(2) skeleton: N-O = 1.392(18) A, O-N = 1.597(16) A, (N=O)(mean) = 1.192(4) A, N-O-N = 106.9(25) degrees, O=N=O = 138.4(24) degrees. The extremely long O-N distance is rationalized by very weak bonding between the two stable radicals (CF(3))(2)NO and NO(2). Whereas the ab initio methods HF (O-N = 1.395 A) and MP2 (O-N = 1.664 A) fail to reproduce this bond length correctly, the hybrid method B3LYP (O-N = 1.584 A) results in good agreement.

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PubMed2002

Tribromohydroxyphosphonium hexafluorometalate: synthesis, spectroscopic characterization, and crystal structure of Br(3)POH(+)AsF(6)(-).

The reaction of tribromophosphine oxide in the superacidic systems XF/MF(5) (X = H, D; M = As, Sb) leads to tribromohydroxyphosphonium hexafluorometalates. The structure was successfully elucidated in the case of tribromohydroxyphosphonium hexafluoroarsenate. Br(3)POH(+)AsF(6)(-) crystallizes in the orthorhombic space group Pnma (No. 53 with a = 1292.5(1) pm, b = 871.6(1) pm, and c = 845.0(1) pm) with four formula units per cell. The Raman, IR, (1)H NMR, and (31)P NMR spectra of Br(3)POX(+)MF(6)(-) (X = H, D; M = As, Sb) are reported.

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PubMed1999

Undecafluorodiarsenate Anion: Synthesis and Crystal Structure of (MeS)(2)CSH(+)As(2)F(11)(-).

Dimethyltrithiocarbonate reacts with the superacidic systems HF/MF(5) and DF/MF(5) (M = As, Sb) to form (MeS)(2)CSX(+)MF(6)(-) (X = H, D). With an excess of AsF(5) the reaction leads to (MeS)(2)CSX(+)As(2)F(11)(-) (X = H, D). The latter salt crystallizes in the monoclinic space group P2(1)/c (No. 14 with a = 7.687(1) Å, b = 21.327(6) Å, c = 8.704(1) Å, and beta = 91.99(1) degrees ) with four formula units per cell. The undecafluorodiarsenate anion contains an As-F-As bridge with two As-F bonds significantly longer than the nonbridging bonds and an As-F-As angle of 159.1(6) degrees. The Raman, IR, and (1)H, (75)As, (19)F, and (13)C NMR spectra of (MeS)(2)CSX(+)SbF(6)(-) and (MeS)(2)CSX(+)As(2)F(11)(-) (X = H, D) are reported.

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PubMed1999

A New Method for Preparation and Crystal Structure of (Trifluoromethyl)iodine Dichloride.

(Trifluoromethyl)iodine dichloride (CF(3)ICl(2)) is synthesized by the reaction of (trifluoromethyl)iodine chloride fluoride (CF(3)I(Cl)F) with trimethylchlorosilane ((CH(3))(3)SiCl) at -40 degrees C. By using this route of preparation, in which CF(3)I(Cl)F undergoes a chlorine-fluorine exchange, CF(3)ICl(2) can be obtained in high purity and yield. CF(3)ICl(2) crystallizes in the orthorhombic space group Cmca with a = 6.990(1) Å, b = 7.985(1) Å, c = 21.177(1) Å, and eight formula units per unit cell. The final R indices [I > 2sigma(I)] are R(1) = 0.0341 and wR(2) = 0.0631. CF(3)ICl(2) is, in contrast to iodine trichloride (ICl(3)), monomeric, and its molecular structure is T-shaped with the CF(3) group in the equatorial position. The Raman, IR, and NMR spectra are also described.

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PubMed1999

Halogenated Carboxonium Salts: Preparation and Structural Analysis.

We have studied the preparation and isolation of the halogenated alkylidene oxonium salts CH(3)OCHX(+)MF(6)(-) (X = Cl, F; M = As, Sb). Addition of dichloromethylmethylether at -78 degrees C to the superacidic media HF/MF(5) resulted in the formation of the chlorine compounds CH(3)OCHCl(+)MF(6)(-), whereas at -65 degrees C the fluorinated salts CH(3)OCHF(+)MF(6)(-) are formed by a chlorine/fluorine exchange. The salts are characterized by their low-temperature IR and Raman spectra. Additionally, the crystal structures of the hexafluoroantimonates are presented. The structures of the cations turned out to be different in some points. The salt CH(3)OCHF(+)SbF(6)(-) crystallizes in the monoclinic space group P2(1)/c with 4 molecules in the unit cell and a = 9.942(2), b = 7.454(2), and c = 10.297(3) Å; beta = 111.27(2) degrees. The salt CH(3)OCHCl(+)SbF(6)(-) crystallizes in the monoclinic space group P2(1)/c with 4 formula in the unit cell and a = 5.970(3), b = 12.019(5), and c = 10.994(5) Å; beta = 92.59(3) degrees.

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PubMed1998

On the Reaction of Phosphorous Acid with Superacids and the Crystal Structure of H(5)O(2)(+)SbF(6)(-) and Me(4)N(+)HPF(5)(-).

Phosphorous acid reacts with the superacidic system HF/SbF(5) with formation of HPF(4), water, and oxonium hexafluoroantimonate, which crystallizes as H(5)O(2)(+)SbF(6)(-) in the triclinic space group P&onemacr; with a = 6.492(6) Å, b = 7.469(8) Å, c = 8.095(6) Å, alpha = 116.17(7) degrees, beta = 93.90(7) degrees, and gamma = 112.34(7) degrees, with two formula units per unit cell. The unit cell contains two H(5)O(2)(+) ions of approximate symmetry C(2)(h)() with an intramolecular O.O distance of 2.418(8) or 2.40(1) Å, respectively. The reaction is discussed with regard to the formation of protonated species in various superacidic media. In addition the crystal structure of Me(4)N(+)HPF(5)(-) which is formed by the reaction of HPF(4) with Me(4)N(+)F(-) is reported. The salt crystallizes in the tetragonal space group P4/nmm with a = 8.564(5) Å and c = 5.687(2) Å, with two formula units per unit cell. The P-F distances of P-F(eq) = 1.595(6) Å and P-F(ax) = 1.594(9) Å for the psi-octahedral HPF(5)(-) show no significant interaction exercised by hydrogen on the cis- and trans-fluorine.

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PubMed1997

Trifluoromethyl Hypobromite, CF(3)OBr.

The synthesis and isolation of the hypobromite CF(3)OBr is reported. CF(3)OBr is formed besides Me(4)N(+)BrF(2)(-) by the reaction of CF(3)OCl and Me(4)N(+)Br(3)(-) via an addition-elimination mechanism. The initially formed solid, [2CF(3)OBr.Me(4)N(+)BrF(2)(-)], was characterized by (13)C and (19)F NMR, Raman, IR, and mass spectra. The hypobromite was separated from the solid by high-vacuum condensation onto a cold surface and characterized by matrix isolation multichannel Raman spectroscopy. An ab initio calculation was performed, and a force field and the torsional barrier of CF(3)OBr were calculated. The calculation predicts an eclipsed conformation with a rotional barrier of 3.4 kcal/mol. The photolytic decomposition of CF(3)OBr in the solid state and in an argon matrix was investigated.

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