- Award ID(s):
- 1954310
- PAR ID:
- 10419953
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 24
- Issue:
- 42
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 25895 to 25903
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The possibility of the transfer of the TH 3 group across a tetrel bond is considered by ab initio calculations. The TB is constructed by pairing PhTH 3 (Ph = phenyl; T = Si and Ge) with bases NH 3 , NHCH 2 , and the C 3 N 2 H 4 carbene. The TH 3 moves toward the base but only by a small amount in these dimers. However, when a Be 2+ or Mg 2+ dication is placed above the phenyl ring, the tetrel bond strength is greatly magnified reaching up to nearly 100 kcal mol −1 . This dication also induces a much higher degree of transfer which can be best categorized as half-transfer for the two N-bases and a near complete transfer for the carbene.more » « less
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Abstract The T⋅⋅⋅N tetrel bond (TB) formed between TX3OH (T=C, Si, Ge; X=H, F) and the Lewis base N≡CM (M=H, Li, Na) is studied by ab initio calculations at the MP2/aug‐cc‐pVTZ level. Complexes involving TH3OH contain a conventional TB with interaction energy less than 10 kcal/mol. This bond is substantially strengthened, approaching 35 kcal/mol and covalent character, when fluorosubstituted TF3OH is combined with NCLi or NCNa. Along with this enhanced binding comes a near equalization of the TB T⋅⋅⋅N and the internal T−O bond lengths, and the associated structure acquires a trigonal bipyramidal shape, despite a high internal deformation energy. This structural transformation becomes more complete, and the TB is further strengthened upon adding an electron acceptor BeCl2to the Lewis acid and a base to the NCM unit. This same TB strengthening can be accomplished also by imposition of an external electric field.
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The tetrel bond (TB) between 1,2-benzisothiazol-3-one-2-TF3-1,1-dioxide (T = C, Si) and the O atom of pyridine-1-oxide (PO) and its derivatives (PO-X, X = H, NO2, CN, F, CH3, OH, OCH3, NH2, and Li) is examined by quantum chemical means. The Si∙∙∙O TB is quite strong, with interaction energies approaching a maximum of nearly 70 kcal/mol, while the C∙∙∙O TB is an order of magnitude weaker, with interaction energies between 2.0 and 2.6 kcal/mol. An electron-withdrawing substituent on the Lewis base weakens this TB, while an electron-donating group has the opposite effect. The SiF3 group transfers roughly halfway between the N of the acid and the O of the base without the aid of cooperative effects from a third entity.
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Abstract Crystal structures document the ability of a TF3group (T=Si, Ge, Sn, Pb) situated on a naphthalene system to engage in an intramolecular tetrel bond (TB) with an amino group on the adjoining ring.
Ab initio calculations evaluate the strength of this bond and evaluate whether it can influence the ability of the T atom to engage in a second, intermolecular TB with another nucleophile. A very strong CN−anionic base can approach the T either along the extension of a T−C or T−F bond and form a strong TB with an interaction energy approaching 100 kcal/mol, although this bond is weakened a bit by the presence of the internal T⋅⋅⋅N bond. The much less potent NCH base engages in a correspondingly longer and weaker TB, less than 10 kcal/mol. Such an intermolecular TB is weakened by the presence of the internal TB, to the point that it only occurs for the two heavier tetrel atoms Sn and Pb. -
The π-hole above the plane of the X 2 T′Y molecule (T′ = Si, Ge, Sn; X = F, Cl, H; Y = O, S) was allowed to interact with the TH hydride of TH(CH 3 ) 3 (T = Si, Ge, Sn). The resulting TH⋯T′ tetrel bond is quite strong, with interaction energies exceeding 30 kcal mol −1 . F 2 T′O engages in the strongest such bonds, as compared to F 2 T′S, Cl 2 T′O, or Cl 2 T′S. The bond weakens as T′ grows larger as in Si > Ge > Sn, despite the opposite trend in the depth of the π-hole. The reverse pattern of stronger tetrel bond with larger T is observed for the Lewis base TH(CH 3 ) 3 , even though the minimum in the electrostatic potential around the H is nearly independent of T. The TH⋯T′ arrangement is nonlinear which can be understood on the basis of the positions of the extrema in the molecular electrostatic potentials of the monomers. The tetrel bond is weakened when H 2 O forms an O⋯T′ tetrel bond with the second π-hole of F 2 T′O, and strengthened if H 2 O participates in an OH⋯O H-bond.more » « less