The π‐Tetrel Bond and its Influence on Hydrogen Bonding and Proton Transfer

Abstract

The positive region that lies above the plane of F TO (T=C and Si) interacts with malondialdehyde (MDA), which contains an intramolecular H-bond. The T atom of F TO can lie either in the MDA molecular plane, forming a T⋅⋅⋅O tetrel bond, or F TO can stack directly above MDA in a parallel arrangement. The former structure is more stable than the latter, and in either case, F SiO engages in a much stronger interaction than does F CO, reaching nearly 200 kJ mol . The π-tetrel bond strengthens/weakens the MDA H-bond when the bond is formed to the hydroxyl/carbonyl group of MDA, and causes an accompanying inhibition/promotion of proton transfer within this H-bond; this effect is stronger for F SiO. These same aspects can be tuned by substituents placed on any of the C atoms of MDA, although their effects are not fully correlated with the electron-withdrawing or electron-releasing properties of the substituent. A new type of π-π tetrel bond occurs when the π-hole on the T atom of F TO approaches the middle carbon atom of MDA from above, and a similar configuration is also found between F TO and benzene. Evidence for extensive C⋅⋅⋅C π-π tetrel bonding in crystal materials is presented.

Comparison of σ‐/π‐Hole Tetrel Bonds between TH3F/F2TO and H2CX (X=O, S, Se)

“…Furthermore, the O⋅⋅⋅C interaction is stronger than the Si⋅⋅⋅X interaction. The similar π‐π structure was also reported in the complex between F 2 TO and benzene . For each complex between F 2 TO and benzene, two π‐π structures are present, both of them having similar stability for F 2 CO but different interaction energies for F 2 SiO …”

“…In the almost same period, Grabowski systematically performed a theoretical study of tetrel bonding in chemical reactions and claimed that it plays a role of a preliminary stage in the S N 2 reaction. Followed by these studies, more attention has been focused on the structures, properties, nature, and applications of tetrel bonds in different systems …”

“…H 2 CX forms a σ‐hole tetrel bond with TH 3 F but a π‐hole tetrel bond with F 2 TO. The π‐hole tetrel‐bonded complexes were also reported in different systems although their study is relatively scarce against with the σ‐hole complexes. Complexes between heavy tetrel donors TF 4 (T=Sn, Pb) and NH 4 /HCN were studied at the MP2/aug‐cc‐pVTZ level and hypervalency phenomenon was observed for these complexes .…”

Quantitative Assessment of Tetrel Bonding Utilizing Vibrational Spectroscopy

“…The formation of tetrel bonds can be understood as an interaction between an electron-deficient tetrel atom of a Lewis acid (tetrel donor, T-donor) and an electron-rich of a Lewis base (tetrel acceptor, T-acceptor) (see Figure 1 ) [ 53 ]. The Lewis base (T-acceptor) can be any electron-rich entity possesing a lone pair [ 60 , 61 , 62 , 63 ], a -system [ 55 , 64 ], an anion [ 44 , 65 ], etc. To explain the formation of a tetrel bond via -hole interactions, Politzer, Murray, and Clark suggested an interaction between a region of positive electrostatic potential as a result of diminished electron density on the tetrel atom (T-donor) and a region of negative electrostatic potential on an electron-rich atom (T-acceptor) [ 3 , 58 , 66 , 67 , 68 ].…”

Ability of IR and NMR Spectral Data to Distinguish between a Tetrel Bond and a Hydrogen Bond

“…In the case of the C atom, its ability to engage in a TB has typically been amplified by adding a number of electron-withdrawing substituents like F [27][28][29] rather than considering a CH3 group itself. Our own lab has contributed to the current understanding of tetrel bonding as well [30][31][32][33][34][35] including the issue of steric crowding 26,36 and the manner in which such interactions might be used to design an effective selective anion receptor [37][38][39][40] . In sum, like their noncovalent bonding counterparts, TBs are strengthened by electron-withdrawing substituents whose polarization induces a more positively charged central atom.…”