Tetrel Bond between 6-OTX(3)-Fulvene and NH(3): Substituents and Aromaticity

Carbon bonding is a weak interaction, particularly when a neutral molecule acts as an electron donor. Thus, there is an interesting question of how to enhance carbon bonding. In this paper, we found that the –OCH(3) group at the exocyclic carbon of fulvene can form a moderate carbon bond with NH(3) with an interaction energy of about −10 kJ/mol. The –OSiH(3) group engages in a stronger tetrel bond than does the –OGeH(3) group, while a reverse result is found for both –OSiF(3) and –OGeF(3) groups. The abnormal order in the former is mainly due to the stronger orbital interaction in the –OSiH(3) complex, which has a larger deformation energy. The cyano groups adjoined to the fulvene ring not only cause a change in the interaction type, from vdW interactions in the unsubstituted system of –OCF(3) to carbon bonding, but also greatly strengthen tetrel bonding. The formation of tetrel bonding has an enhancing effect on the aromaticity of the fulvene ring.