A theoretical evaluation for new fused remote N‐heterocyclic silylenes (RNHSis) using density functional theory

Abstract

AbstractIn this research, we compare and contrast the stability, polarity, polarizability, band gap, and global reactivity of singlet (s) and triplet (t) fused benzene N‐heterocyclic silylene (1‐s and 1‐t) along with five numbered congeners (2x‐s, and 2x‐t, x = CH2, SiH2, GeH2, NH, PH, AsH, O, S, and Se) at DFT (density functional theory). All singlet and triplet remote N‐heterocyclic silylenes (RNHSis) appear as minima showing positive force constant. Every singlet RNHSi emerges as ground state and exhibits more stability than its corresponding triplet RNHSi. In going from 1‐s to 2x‐s species, the thermodynamic and kinetic stability is increased, so that higher ΔEs‐t (= Et − Es) and higher band gap or ΔEHOMO–LUMO (=ELUMO − EHOMO) is considered for 2CH2‐s, 2NH‐s, and 2O‐s structures. In going from second row to forth row of every group in the periodic table, electronegativity of heteroatoms have pronounced effect on the stability, polarity, polarizability, and band gap of 2x‐s species. These silylenes show more stability than the synthesized silylene by Kira. Every 2x‐t silylene shows higher nucleophilicity (about 1.6 times) than its corresponding 2x‐s analogous. Every singlet RNHSi reveals lower nucleophilicity (N), higher electrophilicity (ω), chemical potential (μ), and global hardness (η) than its triplet congener. Furthermore, 2x‐s silylenes benefit from stabilization effect of two heteroatoms synchronously in the fused five‐membered ring via mesomeric effect and π donation from the lone pairs of heteroatom to the formally vacant 3p orbital of the silylenic center. Hence, we predict higher stability as well as lower global reactivity of RNHSis than Kira's silylene will make them creditable for the synthetic research.