Low pressure gas electron diffraction: An experimental setup and case studies.

Vishnevskiy Y, Blomeyer S, Reuter C. Low pressure gas electron diffraction: An experimental setup and case studies. The Review of scientific instruments. 2020;91(7): 074104.Principles of low pressure gas electron diffraction are introduced. An experimental setup has been constructed for measuring the electron diffraction patterns of gaseous samples at pressures below 10-3 mbar. Test measurements have been performed for benzoic acid at T = 287 K corresponding to a vapor pressure of the substance P = 2 * 10-4 mbar, for iodoform CHI3 at T = 288 K (P = 4 * 10-4 mbar), and for carbon tetraiodide CI4 at T = 290 K (P = 1 * 10-4 mbar). Due to the low experimental temperature, thermal decomposition of CI4 has been prevented, which was unavoidable in previous classical measurements at higher temperatures. From the obtained data, the molecular structures have been successfully refined. The most important semi-empirical equilibrium molecular parameters are re(Car-Car)av = 1.387(5) A in benzoic acid, re(C-I) = 2.123(3) A in iodoform, and re(C-I) = 2.133(7) A in carbon tetraiodide. The determined parameters showed consistency with the theoretically predicted values. A critical comparison with the results of the earlier investigations has also been done

Direct functionalization of white phosphorus with anionic dicarbenes and mesoionic carbenes: facile access to 1,2,3-triphosphol-2-ides

Rottschäfer D, Blomeyer S, Neumann B, Stammler H-G, Ghadwal R. Direct functionalization of white phosphorus with anionic dicarbenes and mesoionic carbenes: facile access to 1,2,3-triphosphol-2-ides. CHEMICAL SCIENCE. 2019;10(48):11078-11085.A series of unique C2P3-ring compounds [(ADC(Ar))P-3] (ADC(Ar) = ArC{(DippN)C}(2); Dipp = 2,6-iPr(2)C(6)H(3); Ar = Ph 4a, 3-MeC(6)H(4)4b, 4-MeC(6)H(4)4c, and 4-Me(2)NC(6)H(4)4d) are readily accessible in an almost quantitative yield by the direct functionalization of white phosphorus (P-4) with appropriate anionic dicarbenes [Li(ADC(Ar))]. The formation of 1,2,3-triphosphol-2-ides (4a-4d) suggests unprecedented [3 + 1] fragmentation of P-4 into P-3(+) and P-. The P-3(+) cation is trapped by the (ADC(Ar))(-) to give 4, while the putative P- anion reacts with additional P-4 to yield the Li3P7 species, a useful reagent in the synthesis of organophosphorus compounds. Remarkably, the P-4 fragmentation is also viable with the related mesoionic carbenes (iMICs(Ar)) (iMIC(Ar) = ArC{(DippN)(2)CCH}, i stands for imidazole-based) giving rise to 4. DFT calculations reveal that both the C3N2 and C2P3-rings of 4 are 6 pi-electron aromatic systems. The natural bonding orbital (NBO) analyses indicate that compounds 4 are mesoionic species featuring a negatively polarized C2P3-ring. The HOMO-3 of 4 is mainly the lone-pair at the central phosphorus atom that undergoes sigma-bond formation with a variety of metal-electrophiles to yield complexes [{(ADC(Ar))P-3}M(CO)(n)] (M = Fe, n = 4, Ar = Ph 5a or 4-Me-C(6)H(4)5b; M = Mo, n = 5, Ar = Ph 6; M = W, n = 5, Ar = 4-Me(2)NC(6)H(4)7)

Isolation of singlet carbene derived 2-phospha-1,3-butadienes and their sequential one-electron oxidation to radical cations and dications

A synthetic strategy for the 2-phospha-1,3-butadiene derivatives [{(IPr)C(Ph)}P(cAAC$^{Me}$)] (3a) and [{(IPr)C(Ph)}P(cAAC$^{Cy}$)] (3b) (IPr = C{(NDipp)CH}$_{2}$, Dipp = 2,6-iPr$_{2}$C$_{6}$H$_{3}$; cAAC$^{Me}$ = C{(NDipp)CMe$_{2}$CH$_{2}$CMe$_{2}$}; cAAC$^{Cy}$ = C{(NDipp)CMe$_{2}$CH$_{2}$C(Cy)}, Cy = cyclohexyl) containing a C=C–P=C framework has been established. Compounds 3a and 3b have a remarkably small HOMO–LUMO energy gap (3a: 5.09; 3b: 5.05 eV) with a very high-lying HOMO (-4.95 eV for each). Consequently, 3a and 3b readily undergo one-electron oxidation with the mild oxidizing agent GaCl$_{3}$ to afford radical cations [{(IPr)C(Ph)}P(cAAC$^{R}$)]GaCl$_{4}$ (R = Me 4a, Cy 4b) as crystalline solids. The main UV-vis absorption band for 4a and 4b is red-shifted with respect to that of 3a and 3b, which is associated with the SOMO related transitions. The EPR spectra of compounds 4a and 4b each exhibit a doublet due to coupling of the unpaired electron with the $^{31}$P nucleus. Further oneelectron removal from the radical cations 4a and 4b is also feasible with GaCl$_{3}$, affording the dications [{(IPr)C(Ph)}P(cAAC$^{R}$)](GaCl$_{4}$)$_{2}$ (R = Me 5a, Cy 5b) as yellow crystals. The molecular structures of compounds 3–5 have been determined by X-ray diffraction and analyzed by DFT calculations

Phasenabhängige Strukturchemie - Struktur-Reaktivitäts-Beziehungen und nicht-kovalente Wechselwirkungen

Blomeyer S. Phasenabhängige Strukturchemie - Struktur-Reaktivitäts-Beziehungen und nicht-kovalente Wechselwirkungen. Bielefeld; 2017

Gas standards in gas electron diffraction: accurate molecular structures of CO2 and CCl4

Vishnevskiy Y, Blomeyer S, Reuter C. Gas standards in gas electron diffraction: accurate molecular structures of CO2 and CCl4. STRUCTURAL CHEMISTRY. 2019;31(2):667-677.Equilibrium and vibrationally averaged structures of CO2 have been determined using combination of available experimental rotational constants and high level quantum-chemical calculations. Gas electron diffraction patterns of CO2 and CCl4 have been measured and analyzed. A method for fine control of electron diffraction background smoothness is proposed. The patterns of CO2 were used for calibration of electron wavelength. From the patterns of CCl4, molecular structure has been refined. The determined, in this work, parameters can be recommended as reference values in calibration of gas electron diffraction experiments. For CO2, these values are r(a)(C=O) = 1.1641 (1), r(a)(O...O) = 2.3241 (1), l(C=O) = 0.0358 (2), l(O...O) = 0.0473 (4) angstrom, c(3)(C=O) = 3.12 x 10(- 6), c(3)(O...O) = 2.88 x 10(- 6) angstrom(3). The values for CCl4 are r(a)(C-Cl) = 1.7665 (7), r(a)(Cl...Cl) = 2.8828 (12), l(C-Cl) = 0.0502 (4), l(Cl...Cl) = 0.0721 (3) angstrom, and c(3)(C-Cl) = 0.0, c(3)(Cl...Cl) = 0.0 angstrom(3)

Gas electron diffraction of increased performance through optimization of nozzle, system design and digital control

Reuter C, Vishnevskiy Y, Blomeyer S, Mitzel NW. Gas electron diffraction of increased performance through optimization of nozzle, system design and digital control. Zeitschrift fuer Naturforschung, B: A Journal of Chemical Sciences. 2016;71(1):1-13.A no. of measures to increase the quality of data recorded with an improved Balzers Eldigraph KD-G2 gas-phase electron diffractometer are discussed. The beam-stop has been decoupled from the sector enabling us recording the current of the primary beam and scattered electrons during the expt. Different beam-stops were tested for use in the present setup. Modifications of the nozzle tip of an earlier described medium temp. nozzle are reported. The measures lead to reduced exposure times and reduced amt. of sample necessary for complete data collection. [on SciFinder(R)

The nature of interactions of benzene with CF3I and CF3CH2I

Bujak M, Stammler H-G, Blomeyer S, Mitzel NW. The nature of interactions of benzene with CF3I and CF3CH2I. Chemical Communications. 2018;55(2):175-178

Trimethylaluminum: Bonding by Charge and Current Topology

Stammler H-G, Blomeyer S, Berger R, Mitzel NW. Trimethylaluminum: Bonding by Charge and Current Topology. Angewandte Chemie-International Edition. 2015;54(46):13816-13820.The charge density distribution of the trimethylaluminum dimer was determined by high-angle X-ray diffraction of a single crystal and quantum-chemical methods and analyzed using the quantum theory of atoms in molecules. The data can be interpreted as Al2Me6 being predominantly ionically bonded, with clear indications of topological asymmetry for the bridging AlC bonds owing to delocalized multicenter bonding. This interpretation is supported by the calculated magnetic response currents. The data shed new light on the bonding situation in this basic organometallic molecule, which was previously described by contradicting interpretations of bonding

Front Cover: Silylene-Functionalized N-Heterocyclic Carbene (Si−NHC) (Chem. Eur. J. 2/2018)

Rottschäfer D, Blomeyer S, Neumann B, Stammler H-G, Ghadwal R. Front Cover: Silylene-Functionalized N-Heterocyclic Carbene (Si−NHC) (Chem. Eur. J. 2/2018). Chemistry - A European Journal. 2018;24(2):281-281