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The nuclear magnetic resonance of 133Cs (I=7/2) has been studied at room temperature in the isostructural compounds Cs2CuCl4, Cs2CuBr4, Cs2CoCl4 and Cs2ZnCl4. The nuclear quadrupole coupling tensors and the magnetic shift tensors have been determined at the two inequivalent sites of the unit cell for all complexes. A satisfactory description of the quadrupole coupling (νq ≲ 20 kc) with a point charge model is only possible by reducing the charge on the central ion of the MX4 tetrahedron to +1-1. Large isotropic shifts (up to 0.5%) with smaller anisotropic contributions have been found in the paramagnetic compounds. The diamagnetic Cs2ZnCl4 shows shift up to 0.03% relative to CsCl.
Es wird das Mikrowellenspektrum eines symmetrischen Kreisels (tert.-Butyljodid) untersucht, in dem sich die HFS-Komponenten des Schwingungsgrundzustandes mit denen einiger angeregten Vibrationszustände überlagern. Dabei gelingt es, eine allgemeine Methode zur Analyse eines mit den genannten Schwierigkeiten behafteten Spektrums zu entwickeln. Die Auswertung ergibt im Falle des tert.-Butyljodids folgende Konstanten: e Q q = -1709,5 ± 5,5 MHz, B = 1560,60 ± 0,01 MHz, DJ = 0,20 ± 0,10 kHz, DJK = 0,70 ± 0,07 kHz, rC-J = 2,190 ± 0,005 Å.
Es wird ein quantenmechanisches Näherungsverfahren entwickelt, das die Wechselwirkungsenergie der π -Elektronen im Grundzustand aromatischer Kohlenwasserstoffe praktisch ohne Rechenarbeit aus der Strukturformel abzulesen gestattet. Die Resultate des Verfahrens sind im großen und ganzen ebensogut mit der Erfahrung in Übereinstimmung, wie die Resultate des Slater-Paulingschen Verfahrens. Im Falle des Stoffpaares Anthracen-Phenanthren sind sie den Resultaten des Slater-Paulingschen Verfahrens überlegen. Mit Hilfe des Verfahrens lassen sich die Wechselwirkungsenergien der π- Elektronen für ganze Stoffklassen überblicken. Einige Beispiele hierzu werden mitgeteilt.
CH4 und NH4+werden quantenmechanisch als Pseudo-Neon-Atome nach einer Methode behandelt, die der Slaterschen Methode für Atome entspricht. Die Eigenfunktionen nullter Näherung werden aus Eigenfunktionen eines Zentralproblems aufgebaut. Es er-gibt sich sehr gute Übereinstimmung mit den empirischen Daten über -Atomabstände, Suszeptibilitäten und das C-H-Bindungsmoment.
The mass spectrum and the ion molecule reactions of phosphirane and of mixtures of phosphirane with NH3 , NH2D, NHD2 and ND3 have been studied by ion cyclotron resonance spectrometry. Almost all important product ions are formed by PH-group transfer reactions, where ethene is generated as the neutral particle. Only two of the more abundant ions, the protonated molecule, H2P(CH2)2+ and the ion m/e=63, P2H+, are formed via other reaction pathways. Secondary, tertiary and quarternary product ions with the general formula R(PH)n+ (R: phosphirane fragment, n-1, 2, 3) have been detected.
The molecular ion is proved to have a cyclic structure. Two possible structures of the product ions with two and three phosphorus atoms are discussed: a structure with an open phosphorus chain, leaving the phosphirane ring intact and a ring extended structure, produced by a ring extension reaction of the PH-group.
Several rate constants of the ion molecule reactions of the phosphirane molecular ion are given.
The gas phase ion chemistry of the simplest known phosphorus ylide, trimethylmethylenephosphorane, has been studied in the mass range m/e=2 - 186 and the pressure range 10-7-10-4 Torr. The most abundant product ion, m/e = 104, (CH3)2C2H5PCH2'+ is formed by a methylene group transfer reaction of the molecular ion. Almost all of the other product ions formed from the molecular ion can be subsumed under the general formula (CH3)3PCHPRn+ (R = H, CH3; n=1,2,3). The reactions indicate that the molecular ion has lost its ylide character almost completely. The protonated molecule is formed almost exclusively by a reaction of the fragment ion m/e = 75. This reaction and the CH3PH group transfer reaction indicate a cyclic structure (CH3) HP(CH2)2+ for this ion. A cyclic structure is also assumed for the ion m/e = 73, PC3H6+, which undergoes P and PH transfer reactions. The reactions of the ion m/e = 47 are consistent with the structure CH3PH+. The ICR and mass spectra are given, some metastable decompositions are discussed.
The microwave spectra of SiFBr3 and CH3SiBr have been investigated in the region from 30 to 40 GHz. Assuming reasonable values for dSi-F, dSi-C and the methyl group a least squares analysis of the rotational constants yields dSi-Br ≮Br—Si—Br SiFBr3 (2,171 ± 0,001) A (111,36 ± 0,15)°, CH3SiBr3 (2,175±0,001) A (111,09±0,15)°. A barrier to internal rotation of about 1 kcal/mole is estimated by the intensity method.
The microwave spectra of SiHBr3 and SiDBr3 have been investigated in the region from 28 to 40 GHz. From the rotational constants the following structural parameters were derived by a least square method: dSi-H = (1,494 ± 0,009) A, dSi-Br = (2,170 ± 0,001) Å, ∢Br-Si-Br = (111,36 ± 0,25)0. The results are compared with those obtained for other Si-halogen-compounds.
The microwave spectrum of several symmetric and asymmetric top isotopic species of CH3CCl3 has been studied in the region from 8 to 40 GHz. A least squares analysis of the rotational con-stants gave the following structural parameters : dC-C =(1.541 ±0.001) A, dC-Cl = (1,7712 ± 0.0008) A, dC-H = (1.090 ± 0.002) A, ∢H—C—H= (110.04±0.25) ° , ∢Cl—C—Cl= (109.39 ±0.25) °. A dipole moment of μ = (1.755 ± 0.015) D has been derived from the investigation of the Stark effect of the transition J=4→5 of CH3CCl3335. From intensity measurements the barrier to internal rotation is estimated to be (1740 ± 300) cal/mol. An analysis of the spectrum of CH2DCCl2Cl37 shows conclusively that methylchloroform in its equilibrium configuration has the methyl group staggered with respect to the CCl3-group. It could be shown that there exist two torsional isomers gauche and anti with specific microwave spectra.