Evolution of Electronic Properties along the Path from a Covalent to a Tetrel Bond in the Synthesis of Tetraphenyl Substituted Compounds

The evolution of the electronic characteristics of chemical bonds formed and broken along the path of the bimolecular nucleophilic substitution reaction at a tetrahedral central atom, which is the Tt=C, Si, and Ge atom, is analyzed. For this purpose, the reaction paths of the step-by-step replacement of the chlorine atom with the phenyl fragment are modeled, and the energy characteristics of the equilibrium initial, transition, and final states are obtained within the framework of the DFT. For different reaction centers, which are atoms of the carbon group (Tt), changes in electron density distributions and shifts in the positions of the extremes of the total static and electrostatic potential for the forming C–Tt and breaking Tt–Cl bonds along the reaction path are compared. Quantitative criteria are refined that determine the region of existence of a typical noncovalent tetrel bond Tt…Cl, allowing it to be distinguished from a covalent one. Establishment of the properties of the transition state stabilizing tetrel bond may be useful for monitoring the efficient synthesis of covalent organic framework precursors.