H-Bridged Structures for Tetrahedranes A<sub>4</sub>H<sub>4</sub> (A = C, Si, Ge, Sn, and Pb)

Srinivas, G.; Jemmis, Eluvathingal D.

doi:10.1021/ja972070k

Cited by 20 publications

(23 citation statements)

References 103 publications

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“…42 According to ab initio MO studies at the HF, MP2 and B3LYP levels on tetrahedrane with the 6-31G* basis set, the classical T d structure was found to be more stable than all the other alternatives. 43 In contrast, tetra-tert-butyltetrahedrane prefers T over T d symmetry as follows from a DFT study. 44 More recently, ab initio calculations on tetrahedrane were carried out, and the results indicated that the threemembered rings of tetrahedrane are significantly strained, 45 in line with other studies of correlation energy of the valence electrons and angular strain destabilization of tetrahedrane investigated at the HF and MP2 levels.…”

Section: Tetrahedranementioning

confidence: 91%

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

Krivdin¹

2003

Magnetic Reson in Chemistry

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High-level ab initio calculations of carbon-carbon coupling constants were carried out in tetrahedrane, prismane and cubane using the SOPPA (Second-Order Polarization Propagator Approach) computational scheme, in good agreement with available experimental data. It was found that SOPPA performs perfectly well in combination with Dunning's correlation-consistent basis sets augmented with inner core functions; however, no improvement was observed on adding tight s-functions. The utmost importance of electronic correlation effects decreasing the total values of computed J(C,C) in the title compounds by a factor of ∼2.0-2.5 was found. Unknown values of J(C,C) in the title polyhedranes were predicted with high reliability and the latter were treated in terms of s-characters of carbon-carbon bonds based on the additive scheme of coupling pathways. All three compounds under study showed decreased s-characters of their carbon-carbon bonds, which is the result of their remarkable steric strain.

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Section: Tetrahedranementioning

confidence: 91%

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

Krivdin¹

2003

Magnetic Reson in Chemistry

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“…15,16 According to ab initio and DFT studies, the classical T d structure of unsubstituted tetrahedrane was found to be the most stable. 17 In contrast, based on a DFT study, 18 tetra-tert-butyltetrahedrane prefers T over T d symmetry. Recently, new ab initio calculations on tetrahedrane were carried out, and these data confirmed earlier results 14 indicating that three-membered rings of tetrahedrane are significantly strained.…”

Section: Tetrahedrane (1)mentioning

confidence: 99%

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 10—Carbocages

Krivdin

2004

Magnetic Reson in Chemistry

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A comprehensive theoretical study of nine classical caged polycycloalkanes (tetrahedrane, prismane, homoprismane, quadricyclane, cubane, pentaprismane, hexaprismane, adamantane and diamantane) was carried out with special focus on the structural behavior of their J(C,C) values calculated at the SOPPA level. The structural behavior of J(C,C) in small carbocages is dominated by steric strain whereas in medium-sized polycycloalkanes the J(C,C) values show no marked peculiarities and follow several well-defined structural trends typical of other alicyclic compounds.

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“…As a structural alternative to double bonds, the double hydrogen bridge corresponds to a real minimum on the potential surfaces of disilene, digermene, distannene, and diplumbene. ,, For Ge 2 H 4 it lies about 5 kcal/mol above the double-bonded form, but it happens to be the preferred form for Sn 2 H 4 and Pb 2 H 4 . We wanted to examine whether such a double hydrogen bridge arrangement could be favored here and which kind of interaction takes place when it is coupled with a double bond or with another such bridge.…”

Section: Bicyclobutane and Hydrogen-bridged Isomersmentioning

confidence: 99%

Coupling Trans-Bent Double Bonds in Tetragermabutadiene

Trinquier

Jouany

1999

J. Phys. Chem. A

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The coupling of two trans-bent double bonds is examined theoretically through ab initio calculations on tetragermabutadiene H2GeHGeGeHGeH2. If a trans-bent arrangement is maintained for each GeHGeH2 fragment, there are two ways of coupling two trans-bent units, starting from an s-trans conformation around the central bond. The first one preserves an all-trans arrangement of the four pyramidalized germanium atoms. Along the rotational pathway around the central bond, this configuration has no symmetry (C 1), except for dihedral angles of 0° (C s ) or 180° (C i ). As in butadiene, the potential curve along this coordinate is symmetrical with respect to 0° and 180°, with a preferred s-trans form, t-1 and two equivalent gauche forms, g-1, lying about 3 kcal/mol above in energy (MP4/DZP//SCF/DZP). The s-cis saddle point separating the two gauche forms is higher in energy than the barrier separating the s-trans and gauche forms. In the second coupling scheme, the molecule maintains a C 2 symmetry axis for any torsional angle, but the energy curve no longer exhibits any symmetry along the entire [0−2π] rotational coordinate. As anticipated by simple overlap arguments within the pseudo π orbital set, the two minima, reminiscent of s-trans and gauche arrangements, are both skewed. The gauche conformer, g-2, is now below the trans one, t-2, but still above t-1. The minima g-2 and t-2 are separated by two rotational barriers, depending on the direction of rotation. Interconversion between these coupling configurations proceeds through planar inversion at one GeHGeH2 unit. Two pathways are possible, linking either the two s-trans forms or the two gauche forms. The barrier along both the t-1→t-2 and g-2→g-1 pathways is calculated at 4 kcal/mol, in line with the barrier to planarity found in isolated digermene. In both coupling schemes, adiabatic singlet−triplet separations are calculated at 13 kcal/mol. Intramolecular cyclization of g-2 into the cyclobutene form proceeds with a slight activation barrier, and a large exothermicity of 27 kcal/mol. Alternatives in which one or both double bonds of the butadiene form are replaced by a double hydrogen bridge are not favored. By contrast, the two bond-stretch isomers of the bicyclobutane form are significantly lower in energy than the butadiene forms.

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H-Bridged Structures for Tetrahedranes A₄H₄ (A = C, Si, Ge, Sn, and Pb)

Cited by 20 publications

References 103 publications

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 10—Carbocages

Coupling Trans-Bent Double Bonds in Tetragermabutadiene

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H-Bridged Structures for Tetrahedranes A4H4 (A = C, Si, Ge, Sn, and Pb)

Cited by 20 publications

References 103 publications

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 10—Carbocages

Coupling Trans-Bent Double Bonds in Tetragermabutadiene

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H-Bridged Structures for Tetrahedranes A₄H₄ (A = C, Si, Ge, Sn, and Pb)