Showing papers on "Tetrahedral molecular geometry published in 1982"
TL;DR: In this article, a three parameter coupled Morse oscillator model fitted to the known stretching vibrational energy levels is used to predict the energies of all stretching overtone bands with total quantum number ν ⩽ 5> for the molecules CH4, SiH4, GeH4 and their deuterium and 13C isotopic substituents.
Abstract: A three parameter coupled Morse oscillator model fitted to the known stretching vibrational energy levels is used to predict the energies of all stretching overtone bands with total quantum number ν ⩽ 5> for the molecules CH4, SiH4, GeH4 and their deuterium and 13C isotopic substituents. Close local mode degeneracies, with splittings of 3 cm-1 or less, are predicted at the highest energies for all molecules except CD4. Such degeneracies prevail at all excitation levels for SiH4 and GeH4, but those for ν ⩽ 3> are removed by deuterium substitution. The overtone splitting patterns of different molecules and the effects of isotopic substitution are rationalized by means of a correlation diagram, in which the ratio of bond anharmonicity to interbond coupling strength is used to rank the molecules on a scale running from local mode to harmonic normal mode limits. The ranking by local mode character is GeH4 > SiH4 > GeD4 > CH4 > SiD4 > CD4. A model intensity calculation for CH4 confirms the local mode picture wi...
174 citations
TL;DR: In this paper, a theoretical model for the rovibrational analysis of clustered vibrational states for tetrahedral molecules is presented, which reproduces qualitatively and quantitatively the rotational fine structure of the upper levels in the full range of J′ values including level crossings.
60 citations
50 citations
TL;DR: The 3s 1 A 1 Rydberg ground state of the ammonium radical is predicted from UHF/UMP3 calculations using an extensive basis set to have a tetrahedral geometry ( r e = 1.02 A), but to undergo dissociation by tunneling through a low barrier (5300 cm −1 ) to H + NH 3. Dissociation paths to H 2 + NH 2 (C 2v, C s ) were also studied, but no transition states of comparably low energy were found.
34 citations
TL;DR: In this article, the crystal structures of the title compounds have been determined, and the structure is the first example of a truly monomeric trihalogenomercurate (II) anion with distorted tetrahedral geometry about the mercury atoms.
Abstract: The crystal structures of the title compounds have been determined. Crystals of [NBun4](HgCl3) are triclinic, space group P(no. 2) with a= 11.011 (3), b= 11.267(3), c= 19.341(5)A, α= 87.33(2), β= 102.70(2), γ= 96.45(2)°, and Z= 4. The final R value was 0.034 for 2 187 observations. The structure is the first example established where (HgCl3)– is solely in the form of dimeric [Hg2Cl6]2– doubly chloride-bridged anions with distorted tetrahedral geometry about the mercury atoms; these anions are not centrosymmetric and although the terminal Hg–Cl bond lengths are not significantly different from one another (2.38 ± 0.01 A) the bridge is asymmetric with bond lengths 2.665± 0.01 and 2.57 ± 0.02 A. Crystals of [NBun4](HgI3) are tetragonal, space group I2d(no. 122) with a= 13.790(5), c = 26.537(5)A, and Z = 8. The final R value was 0.059 for 1 189 independent intensities measured at 200 K. The structure consists of discrete [NBun4]+ cations and [HgI3]– anions. One Hg–I bond lies on a crystallographic two-fold axis and is of length 2.683(2)A; the other two bonds are not significantly different [2.688(2)A] but make an interbond angle of 115° giving the anion C2v and not D3h symmetry. The closest approach between atoms of different anions is ca. 7.4 A precluding any significant polymeric interaction and making this the first example containing a truly monomeric trihalogenomercurate(II) anion. The [NBun4]+ groups show the expected regular tetrahedral arrangement of bonds around the N atom, but each of the n-butyl chains has the C atoms approximately co-planar, and the ion as a whole is crystallographically constrained to C2 symmetry. Vibrational spectra are rationalised in the light of the crystal structures and indicate that the anion of [NBun4](HgBr3) is dimeric [Hg2Br6]2–. The spectral detail is greatly enhanced in measurements at low temperature (ca. 100 K), especially for the dimeric anions. The structural variety shown by trihalogenomercurates is discussed.
33 citations
TL;DR: In this paper, the crystal structure determinations of the non-isomorphous salts, Cu(1,4-thioxane)3(ClO4) and Cu( 1,4thioxanes)4(BF4) were carried out and the former was shown to contain strongly coordinated perchlorate while the latter contained ionic tetrafluoroborate.
Abstract: Crystal structure determinations of the non-isomorphous salts, Cu(1,4-thioxane)3(ClO4) and Cu(1,4-thioxane)4(BF4) were carried out. The former compound was shown to contain strongly coordinated perchlorate while the later contains ionic tetrafluoroborate. For the coordinated perchlorate group, Cu-O is 2.278(8) A. A third compound, Cu(1,4-thioxane)3(H2O)(BF4), was also characterized by x-ray crystallography, and contains a coordinated water molecule (with Cu-O 2.234(7) A) that is hydrogen bonded to ionic tetrafluoroborate. All three complexes have approximately tetrahedral geometry. The copper(I) atom is coordinated to the sulfur atoms of the 1,4-thioxane rings. In each of the complexes, one of the 1,4-thioxane six-membered rings is coordinatedvia an equatorial ring position and the remaining two or three rings are coordinatedvia an axial position. The compound, Cu(1,4-thioxane)4(ClO4), was also prepared and found to be isomorphous with Cu(1,4-thioxane)4 (BF4), enabling a comparison to be made between the i.r. spectra of ionic and coordinated perchlorate in similar complexes.
20 citations
15 May 1982
TL;DR: In this article, the octupole induced dicole moment correlation functions of liquid CH 4, CF 4 and CCl 4 were measured in the range between 15 and 200 cm −1
Abstract: The far infrared absorption spectra of liquid CH 4 , CF 4 and CCl 4 were measured in the range between 15 and 200 cm −1 The octupole induced dicole moment correlation functions of these liquids and of liquid CBr 4 , which was recalculated from literature data, were compared to the corresponding theoretical correlation functions obtained by molecular dynamics simulation and by analytical theory. At short times(0.05 ps in CH 4 and 0.2 ps in CCl 4 ) the experimental correlation function follows the model reorientational correlation functions. At longer times this is no more the case and the dynamics coherence observed is qualitatively interpreted in terms of a structural correlation in the liquids.
19 citations
TL;DR: In this paper, computer simulations of tetrahedral molecules have been used to test some common models for molecular reorietation in liquids, including the Fokker-Planck and J-diffusion models and a three-term Mori approximation.
13 citations
TL;DR: The compounds bis[N-(2,6-diisopropylphenyl)salicylideneaminato]cobalt(II) and analogous species with substituents at the 5 position of the salicyl moiety have been synthesized.
Abstract: The compounds bis[N-(2,6-diisopropylphenyl)salicylideneaminato]cobalt(II) and analogous species with substituents at the 5-position of the salicyl moiety have been synthesized. They prefer the tetra-coordinate tetrahedral geometry in non-donor solvents, while some of them are forced into planar structures in the solid state. In pyridine, exclusively predominant species are five-coordinate complexes with the base bound with the cobalt(II) ion. Monopyridine adducts, which consist of five-coordinate complexes, have been isolated as crystals.
3 citations
TL;DR: In this article, the spectral properties of cobalt(II) halides with trimethylphosphine oxide (TMPO) and CoCl2.2O2 were investigated for polycrystalline samples and band assignments for TMPO ligand fundamentals were made for a C3v local symmetry.
Abstract: The infrared spectra (4000–150 cm−1) of molecular complexes of cobalt(II) halides with trimethylphosphine oxide (TMPO), CoCl2.2TMPO, Cobr2.2TMPO and Col2.2TMPO, are investigated for polycrystalline samples. The band assignments for TMPO ligand fundamentals are made for a C3v local symmetry. The skeletal stretching vibrations are assigned in the 450–400 cm−1 region for μ(Co-O) and in the 320–150 cm−1 region for μ(Co-X). The frequency ratios μa(Co-X)/μs(Co-X) are compared with the ratios calculated from G matrix elements √Ga(Co-X)/Gs (Co-X) and result a tetrahedral geometry (C2v symmetry) for the CoX2O2 skeleton. The any characteristic infrared bands in this frequency region. From the relative intensities, the formers are attributable as μaCo-O and the latters as μsCo-O. The observed band positions are quite comparable with those reported for other TMPO complexes.
3 citations
TL;DR: Sch6nberg, Singer, Osch & Hoyer as discussed by the authors determined the X-ray structure of one derivative, namely (1) with R = C6H 5.4, Z = 2, D x = 1.30 Mg m-3; R = 0.047 for 2394 reflections.
Abstract: C23H~sN202, triclinic, P1, a = 9.225 (4), b = 12.982(5), c = 8.286 (2)A, a = 102.11(2), fl = 108.93 (4), ? = 95.53 (3) °, M r = 354.4, Z = 2, D x = 1.30 Mg m-3; R = 0.047 for 2394 reflections. The title compound contains neither an approximate twofold rotation axis nor an approximate mirror plane. One of the N atoms displays a trigonal-planar the other a pyramidal coordination geometry. The tetrahedral geometry of the spiro C atom is significantly flattened. Introduction. Ninhydrin (2) reacts with N,N'-disub- stituted ethylenediamines to yield 1,4-diazaspiro(4.4)- nonanes (R = C2H 5, C6H 5, m-CH3C6H 4, p-CH3C6H 4, p-CH3OC6H4), which exhibit a characteristic deep-red colouration (Sch6nberg, Singer, Osch & Hoyer, 1975; Sch6nberg, Singer, Eschenhof & Hoyer, 1978). The magnetic equivalence of the R groups and the appear- ance of the NCH2CH2N bridge as a sharp singlet in the IH NMR spectra indicate that these molecules must display a twofold symmetry axis or a plane of symmetry in solution. As their colour and long- wavelength UV bands cannot be explained in terms of classical chromophore theory, it was decided to determine the X-ray structure of one derivative, namely (1) with R = C6H 5.
TL;DR: In this article, a qualitative model based on the concept that a dynamic Jahn-Teller effect is operative at room temperature is proposed to explain tetrahedral nickel spectra at low temperature.