A. V. Golubinskii

An electron diffraction study of 3-methyldiaziridine and 1,2-dimethyldiaziridine

Abstract The structures of the title compounds, diaziridines, (the first to be studied in the gas phase) have been determined by electron diffraction. The following principal structural parameters were obtained with the estimated standard deviations parenthesized: 3-methyldiaziridine, N-C = 1.489(9) A, N-N = 1.444(13) A, C-C = 1.505(16) A, C-H = 1.107(5) A, α =∠ (C-C, NCN) = 61.3° (0.9); 1,2-dimethyldiaziridine, (parameters of the cycle CN 2 were assumed from the previous molecule), N-C (methyl) = 1.445(3) A, C-H = 1.108(9) A, ∠ C-N-Me = 112.0° (0.5), the two methyl groups are in the trans position. Vibrational amplitudes were also determined for all important distances.

Gas-phase electron diffraction study of μ4-oxohexa-μ-nitratotetraberyllium

Abstract Gaseous μ 4 -oxohexa-μ-nitratotetraberyllium, Be 4 O(NO 3 ) 6 , has been studied by electron diffraction at a temperature of ≈160°C. The intensity data were analysed in terms of a model having T symmetry. The molecular force field was estimated with the aid of a recently developed procedure to provide a satisfactory fit to 29 experimental frequencies and 39 amplitudes within the framework of a 24-parameter force field model. In the final stage of the structural analysis the amplitudes were varied in groups formed on the basis of spectroscopic calculations. The principal geometrical parameters refined to the following values ( r g structure, bond lengths in A, angles in degrees): BeO 1 (O 1 is the central μ 4 -oxygen atom), 1.665(21); BeO, 1.620(8); NO, 1.185(5); NO, 1.298(4); η (the angle of rotation of the NO 3 group about the twofold axis), 25.2(1.8); ∠ONO, 117.0(0.9) (the uncertainties are presented by 2.5 times the standard deviation values, plus a scale error).

Gas-phase electron diffraction study of tris(trimethylstannyl)amine, N(SnMe3)3

Abstract The geometrical parameters of tris(trimethylstannyl)amine have been determined by gas-phase electron diffraction. The a structure has been refined using mean amplitude values calculated from the force fields of a number of tin derivatives. The experimental data are consistent with a planar bond configuration at the nitrogen in N(SnMe 3 ) 3 . The final set of geometrical parameters is as follows (average bond distances, r g , in A, angles in degrees): SnC 2.166(5), SnN 2.038(3), CH 1.117(17). NSnC 108.5(1.5), SnCH 112.1(1.6). Mean amplitude values have been varied for those distances which give considerable contributions to scattering. The results obtained fill a gap in the knowledge of structures of Group IV element μ-nitrido derivatives. They confirm the conclusion that lowering of ligand MR n electro-negativity weakens the tendency to deviation from planarity in the central fragment NM 3 . This tendency may be considered as a manifestation of the second-order Jahn-Teller effect.

Molecular structure of 1,10-dicarba-closo-decaborane(10), 1,10-C2B8H10, by gas-phase electron diffraction

Abstract The molecular structure of the title compound has been determined by gas-phase electron diffraction, assuming that the C 2 B 8 unit has the form of a bicapped square antiprism ( D 4d symmetry). The amplitudes of vibration and the shrinkage corrections were calculated from the force field transferred mainly from 1,6-C 2 B 4 H 6 . The molecular parameters ( r g , φ α ) and uncertainties (3σ) are: B-C = 1.602(2), B2-B3 (basal) = 1.850(5), B2-B6 (equatorial) = 1.829(4), B-H = 1.164(14), C-H = 1.14(2) and ∠C-B-H = 117.5(1.8)°. Comparisons are made with structural data for other carboranes studied in the gas phase.

Gas phase electron diffraction study of basketene, C10H10

Abstract A gas phase electron diffraction study of the cage hydrocarbon, basketene, is reported. A least squares treatment of molecular intensities has been carried out in terms of a geometrically consistent rα structure. The mean amplitude values and shrinkage corrections have been calculated using the force field parameters estimated from the data on simpler molecules. Structure refinement of the C2v molecular model yields the following parameter values (bond lengths, ra, in nm; angles, rα in degrees): av. 0.1092(8); In addition to the geometric parameters listed, the mean amplitudes for all bonded and C· C nonbonded distances have been determined by the least squares method. All the other amplitudes (C· H and H· H) have been fixed at the values estimated from the spectral data. Comparison of the results obtained with the literature data on similar polycyclic molecules points to the stronger internal strain in the basketene molecule.

Molecular structure of gaseous trimethylgermylformate from electron diffraction

Abstract The molecular structure of trimethylgermylformate (TMGF) has been determined by electron diffraction in the gas phase. The principal parameters, bond lengths ( r a , A), bond and torsional angles (deg) with the least-squares standard deviations in parentheses, are as follows: GeC, 1.919(21); GeO, 1.820(28); CO, 1.213(76); CO, 1.326(42); CH(methyl), 1.109(80); C6H8, 1.12(fixed); GeOC, 117.6(23); OGeC, 104.9(7); GeCH, 109.8(80); OCO, 125.4(59); CGeC, 113.6(7); OCH, 127(fixed); GeOCO, 81.2(63); CGeOC, 35.5(38); HCGeO, 73.2(52). It is found that the GeOCO fragment of TMGF is not planar, and the HCO plane is close to the perpendicular position with respect to the GeOC plane. This result stands out from the series of previously obtained data for similar molecules and suggests that the conformation of TMGF is controlled mainly by steric effects. The conformation of TMGF from electron diffraction is in agreement with molecular mechanics calculations.

Electron diffraction investigation of the structure of the tri(tert-butyl)bromostannane molecules in the gaseous phase

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