Reactivity and Activation Barrier Origins of Heavy ‐Like Molecules Featuring a Group 14═P Double Bond Toward Methyl Iodide: A Chemical Insight

This study examines the reactivity of heavy isocyanide analogs G14 = P‐Rea (cAAC→G14 = P–NHB; G14 = group 14 element) in addition reactions with methyl iodide through M06‐2X‐D3/def2‐TZVP computational analysis. Theoretical insights suggest that the doubly bonded G14═P moiety in heavy isocyanide‐like molecules (G14 = P‐Rea) arises from an electron‐sharing interaction between triplet cAAC→G14 and triplet P–NHB fragments. Our theoretical studies indicate that, except for carbon‐ and silicon‐based isocyanides, the Ge = P, Sn = P, and Pb = P analogs readily undergo addition reactions with CH 3 I via a back‐side S N 2 mechanism. According to EDA‐NOCV and FMO theory, the CH 3 I addition to G14 = P‐Rea is primarily governed by the filled p‐π (G14 = P‐Rea) → vacant σ* (H 3 C–I) orbital interaction, with a minor contribution from the reverse empty p‐π* (G14 = P‐Rea) ← occupied σ (H 3 C–I) interaction. The ASM analysis suggests that the activation barrier for CH 3 I addition to G14 = P‐Rea molecules is mainly dictated by the deformation energy of CH 3 I. Shaik's VBSCD model indicates that the singlet‐triplet energy difference in G14 = P‐Rea can be a key factor in determining the reaction barrier for CH 3 I addition.