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.
Competition between Inter and Intramolecular Tetrel Bonds: Theoretical Studies Complemented by CSD Survey
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.
- Award ID(s):
- 1954310
- NSF-PAR ID:
- 10222557
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemPhysChem
- Volume:
- 22
- Issue:
- 10
- ISSN:
- 1439-4235
- Page Range / eLocation ID:
- p. 924-934
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
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
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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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When attached to a tetrazole, a TtR 3 group (Tt = C, Si; R = H, F) engages in a Tt⋯N tetrel bond (TtB) with the Lewis base NCM (M = Li, Na). MP2/aug-cc-pVTZ calculations find that the Si⋯N TtB is rather strong, more than 20 kcal mol −1 for SiH 3 , and between 46 and 53 kcal mol −1 for SiF 3 . The C⋯N TtBs are relatively weaker, less than 8 kcal mol −1 . All of these bonds are intensified when a BH 3 or BF 3 molecule forms a triel bond to a N atom of the tetrazole ring, particularly for the C⋯N TtB, up to 11 kcal mol −1 . In these triads, the SiR 3 group displaces far enough along the line toward the base that it may be thought of as half transferred.more » « less
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null (Ed.)The tetrel bond (TB) recruits an element drawn from the C, Si, Ge, Sn, Pb family as electron acceptor in an interaction with a partner Lewis base. The underlying principles that explain this attractive interaction are described in terms of occupied and vacant orbitals, total electron density, and electrostatic potential. These principles facilitate a delineation of the factors that feed into a strong TB. The geometric deformation that occurs within the tetrel-bearing Lewis acid monomer is a particularly important issue, with both primary and secondary effects. As a first-row atom of low polarizability, C is a reluctant participant in TBs, but its preponderance in organic and biochemistry make it extremely important that its potential in this regard be thoroughly understood. The IR and NMR manifestations of tetrel bonding are explored as spectroscopy offers a bridge to experimental examination of this phenomenon. In addition to the most common σ-hole type TBs, discussion is provided of π-hole interactions which are a result of a common alternate covalent bonding pattern of tetrel atoms.more » « less
