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.
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Diboron Bonds Between BX 3 (X=H, F, CH 3 ) and BYZ 2 (Y=H, F; Z=CO, N 2 , CNH)
The ability of B atoms on two different molecules to engage with one another in a noncovalent diboron bond is studied by ab initio calculations. Due to electron donation from its substituents, the trivalent B atom of BYZ2(Z=CO, N2, and CNH; Y=H and F) has the ability to in turn donate charge to the B of a BX3molecule (X=H, F, and CH3), thus forming a B⋅⋅⋅B diboron bond. These bonds are of two different strengths and character. BH(CO)2and BH(CNH)2, and their fluorosubstituted analogues BF(CO)2and BF(CNH)2, engage in a typical noncovalent bond with B(CH3)3and BF3, with interaction energies in the 3–8 kcal/mol range. Certain other combinations result in a much stronger diboron bond, in the 26–44 kcal/mol range, and with a high degree of covalent character. Bonds of this type occur when BH3is added to BH(CO)2, BH(CNH)2, BH(N2)2, and BF(CO)2, or in the complexes of BH(N2)2with B(CH3)3and BF3. The weaker noncovalent bonds are held together by roughly equal electrostatic and dispersion components, complemented by smaller polarization energy, while polarization is primarily responsible for the stronger ones.
more » « less- Award ID(s):
- 1954310
- PAR ID:
- 10250175
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemPhysChem
- Volume:
- 22
- Issue:
- 14
- ISSN:
- 1439-4235
- Page Range / eLocation ID:
- p. 1461-1469
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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