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81.
Correlations between the internuclear distances r(M-X), the bond energies E(M-X), and the valence force constants fr for di- and trihalides of Group II–V elements are established. Some missing values are estimated. Ivanovo State Chemical Technological Academy. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 859–875, September–October, 1996. Translated by L. Smolina Ivanovo State Chemical Technological Academy. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 859–875, September–October, 1996.  相似文献   
82.
Combined interpretation of electron diffraction and spectroscopic data for the CeF4 molecule is reported. It is shown that the diffraction pattern corresponds to a tetrahedral structure of the molecule with the following effective configuration parameters (T=1180(50) K): rg(Ce-F)=2.036(5) Å, rg(F-F)=3.312(25) Å, l(Ce-F)=0.074(3) Å, l(F-F)=0.261(17) Å. The total force field of the CeF4 molecule is found in a harmonic approximation. Possible participation of the Ce f-electrons in chemical bonding is discussed.  相似文献   
83.
The vibrational problem for the Y(DPM)3 and Y(DPM)2 molecular forms that are present in the overheated vapor of yttrium tris-dipivaloylmethanate is solved. For this purpose, the experimental Raman spectra of Y(DPM)3 solutions are interpreted. The force field of the Y(DPM)2 radical is estimated on the basis of the force constants determined for Y(DPM)3. Rms vibrational amplitudes and corrections for perpendicular displacements to the internuclear distances of the two molecular forms needed for interpreting electron diffraction data are calculated. Translated fromZhurnal Struktumoi Khimii, Vol. 38, No. 3, pp. 470–479, May–June, 1997.  相似文献   
84.
85.
Belova  N. V.  Dalhus  B.  Girichev  G. V.  Giricheva  N. I.  Haaland  A.  Kuzmima  N. P.  Zhukova  T. A. 《Structural chemistry》2011,22(2):393-399
Structural Chemistry - The molecular structure of tris-2,2,6,6-tetramethyl-heptane-3,5-dione aluminium, or Al(thd)3, has been determined by quantum chemical (DFT) calculations, X-ray...  相似文献   
86.

The molecular structure of N,N′-o-phenylene-bis(salicylideneaminato)copper(II) (Cu(saloph)) was determined using the combination of gas-phase electron diffraction (GED), mass spectrometry, and quantum-chemical calculations. According to both experimental and theoretical approaches the molecule of Cu(saloph) is planar and possesses C 2v symmetry. Main structural parameters determined by GED experiment are the following (total error is given in a brackets): r h1(Cu–N) = 1.960(20) Å, r h1(Cu–O) = 1.913(17) Å, ∠NCuN = 82.7(18)°, ∠OCuO = 91.6(21)°, ∠NCuO = 92.9(9)°. The experimental structural parameters of Cu(saloph) molecules determined by X-ray single crystal analysis and GED experiments were discussed and compared to the theoretical ones.

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87.
A gas electron diffraction study of PrI3 and GdI3 has been carried out in combination with mass spectrometric vapour monitoring at 1110(10) K and 1100(10) K, respectively. Up to 3 mol.% of dimeric species was observed in addition to the dominating monomeric molecules. The change of the thermal-averaged r g configuration parameters of the molecules in the series LaI3 → LuI3 reflects the lanthanide contraction. A low value of the shrinkage δ(I···I) even at such a high temperatures may be considered due to vibration effects in molecule whose equilibrium geometric nuclear structure is planar and which correspond to configurationally averaged 4f n electronic state. B3LYP calculations performed in this study with large core potential for lanthanide atoms also resulted in equilibrium geometry of D 3h symmetry. According to the quantum chemical calculations, the potential function the non-planar vibration is essentially anharmonic, which is therefore to be taken into account to correctly describe nuclear dynamics in molecules such as LnI3.  相似文献   
88.
The molecular structure of axial and equatorial conformers of 1-trifluoromethyl-1-silacyclohexane, (C5H10SiHCF3), as well as the thermodynamic equilibrium between these species was investigated by means of gas electron diffraction (GED), dynamic nuclear magnetic resonance (DNMR) spectroscopy, and quantum chemical calculations (B3LYP, MP2, and CBS-QB3). According to GED, the compound exists as a mixture of two Cs symmetry conformers possessing the chair conformation of the six-membered ring and differing in the axial or equatorial position of the CF3 group (axial=58(12) mol%/equatorial=42(12) mol%) at T=293 K. This result is in a good agreement with the theoretical prediction. This is, however, in sharp contrast to the conformational properties of the cyclohexane analogue. The main structural feature for both conformers is the unusually long exocyclic bond length Si--C 1.934(10) A. A low-temperature 19F NMR experiment results in an axial/equatorial ratio of 17(2) mol%:83(2) mol% at 113 K and a DeltaG (not equal) of 5.5(2) kcal mol-1. CBS-QB3 calculations in the gas-phase and solvation effect calculations using the PCM(B3LYP/6-311G*) and IPCM(B3LYP/6-311G*) models were applied to estimate the axial/equatorial ratio in the 100-300 K temperature range, which showed excellent agreement with the experimental results. The minimum energy pathways for the chair-to-chair inversion of trifluoromethylsilacyclohexane and methylsilacyclohexane were also calculated using the STQN(Path) method.  相似文献   
89.
The molecular structure of nickel(II) and copper(II) N,N′-ethylene-bis(acetylacetoneiminates), NiO2N2C12H18 and CuO2N2C12H18, at 442(5) K and 425(5)K, respectively. Both molecules have C 2 symmetry with a nearly planar MN2O2 coordination site and internuclear distances r h1(M-O) = 1.862(10)/1.923(17) Å and r h1(M-N) = 1.879(10)/1.947(18) Å for Ni(acacen) and Cu(acacen), respectively. The structure of free molecules is close to the structure of molecules in crystal. The DFT/3LYP quantum-chemical calculations (CEP-31G and 6-31G* basis sets) gave a molecular structure that agreed satisfactorily with the one found in experiment. The low-spin 1 A and high-spin 3 A states of the Ni(acacen) molecule were considered. It was found that a change in multiplicity caused significant changes in the geometrical and electronic structure of the MN2O2 coordination site. As shown by experiment and calculations for the NiO2N2C12H18 molecule, the low-spin 1 A state is the ground state. The internal rotation of CH3(CN) and CH3(CO) methyl groups was studied by the 3LYP/CEP-31G method. It was shown that steric hindrances led to a high rotation barrier of the CH3(CN) group.  相似文献   
90.
The geometric structure and conformational properties of the saturated five-membered-ring compound 2,2-di-tert-butyl-1,3-diaza-2-silacyclopentane, (t-Bu)(2)Si(NH)(2)(CH(2))(2), was investigated by gas electron diffraction and quantum chemical methods (B3LYP and MP2 with 6-31G basis sets). The compound exists as a mixture of two conformers, both possessing a twist conformation and C(2) symmetry. In the prevailing form (76(6) % at 305 K) the N-H bonds stagger the adjacent CH(2) groups, and in the minor form the N-H bonds eclipse the CH(2) groups. This conformational mixture corresponds to a free energy difference of DeltaG degrees = 0.69(19) kcal/mol. The B3LYP method predicts a preference for the eclipsed conformer. The largest torsion occurs around the C-C bond with tau(NCCN) = 29.2(24) degrees. The degree of puckering in the title compound is considerably smaller than that in silacyclopentane with tau(CCCC) = 49.7(14) degrees. This has been rationalized by larger angle strain in the title compound.  相似文献   
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