Understanding the Impact of Group 14 Elements on the Reactivity of [1 + 2] Cycloaddition Reaction between a Cyclic (Alkyl)(amino)carbene Analogue with a Group 14 Element and a Heavy Acetylene Molecule.

Computational exploration using the density functional theory framework (M06-2X-D3/def2-TZVP) was undertaken to investigate the [1 + 2] cycloaddition reaction between a five-membered-ring heterocyclic carbene analogue ( G14-Rea ; G14 = group 14 element) and a heavy acetylene molecule ( G14G14-Rea ). It was theoretically observed that exclusively Si-Rea , Ge-Rea , and Sn-Rea demonstrate the capacity to participate in the [1 + 2] cycloaddition reaction with the triply bonded SiSi-Rea . In addition, only three heavy acetylenes ( SiSi-Rea , GeGe-Rea , and SnSn-Rea ) can catalyze the [1 + 2] cycloaddition reaction with Si-Rea . Our theoretical findings elucidated that the reactivity trend observed in these [1 + 2] cycloaddition reactions primarily arise from the deformation energies of the distorted G14G14-Rea . Also, our study reveals that the bonding characteristics of their respective transition states are controlled by the singlet-singlet interaction (donor-acceptor interaction), rather than the triplet-triplet interaction (electron-sharing interaction). Additionally, our work demonstrates that the bonding behavior between G14-Rea and G14G14-Rea is predominantly determined by the filled p -π orbital of G14G14-Rea (HOMO) → the empty perpendicular p -π orbital of G14-Rea (LUMO), rather than the vacant p -π* orbital of G14G14-Rea ( LUMO) ← the filled sp 2 orbital of G14-Rea (HOMO).