Intermolecular Non-Covalent Carbon-Bonding Interactions with Methyl Groups: A CSD, PDB and DFT Study

Abstract

A systematic evaluation of the CSD and the PDB in conjunction with DFT calculations reveal that non-covalent Carbon-bonding interactions with X–CH3 can be weakly directional in the solid state (P ≤ 1.5) when X = N or O. This is comparable to very weak CH hydrogen bonding interactions and is in line with the weak interaction energies calculated (≤ –1.5 kcal·mol−1) of typical charge neutral adducts such as [Me3N-CH3···OH2] (2a). The interaction energy is enhanced to ≤–5 kcal·mol−1 when X is more electron withdrawing such as in [O2N-CH3··O=Cdme] (20b) and to ≤18 kcal·mol−1 in cationic species like [Me3O+-CH3···OH2]+ (8a).

The Effects of Electronegativity of X and Hybridization of C on the X−C⋅⋅⋅O Interactions: A Statistical Analysis on Tetrel Bonding

“…There is an excellent work on tetrel bonding reported by Mooibroek [8] . In this work the author has studied the electronic factor of the tetrel bonding by nullifying the steric as well as geometric factors.…”

Observations of tetrel bonding between sp3-carbon and THF

“…This is much larger than interactions of dimethyl ether halogen bonded to I-C 6 F 5 (À5.6 kcal mol À1 ) or hydrogen bonded to water (À6.7 kcal mol À1 ) at this same level of theory. 37,56 Interestingly, the [1/THF] structure shown in Fig. 2b was found to be 1.1 kcal mol À1 more stable, representing the true energetic minimum with DE ¼ À11.2 kcal mol À1 (see also Fig.…”

“…[29][30][31][32] Non-covalent interactions with sp 3 -hybridized carbon atoms are implicated in the advent of canonical S N 2 nucleophilic displacement reactions 12,[33][34][35] and can persist with methyl groups in crystal structures. [36][37][38] However, a supramolecular synthon to predictably generate directional tetrel-bonding interactions centred on sp 3 -C has not yet been experimentally disclosed. We envisaged that 1,1,2,2tetracyanocyclopropane (TCCP) derivatives could full this role.…”

DFT and IsoStar Analyses to Assess the Utility of σ‐ and π‐Hole Interactions for Crystal Engineering

“…Propane ( 7 ) is hardly polarized (−3 to +11 kcal mol −1 ) and the extremes are not descernable on the color scale used (see Figure S2 for a MEP with alternative scale). Interestingly, the C‐atoms of propane ( 7 ) are most electronegative, suggesting they might act as the de facto ‘electron rich’ site [35b,44] . Most of the HOMOs of 1 , 3 , 6 , 8 and 10 – 12 coinside with the most negative site of the MEPs, which in turn corresponds to a lone‐pair or π electrons.…”