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Breathing viability into cyclonona‐3,5,7‐trienylidenes via α‐dimethyl and ά‐moieties at DFT
Author(s) -
Kassaee M.Z.,
Koohi M.
Publication year - 2013
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3123
Subject(s) - chemistry , singlet state , natural bond orbital , electrophile , carbene , ground state , charge (physics) , density functional theory , computational chemistry , nucleophile , transition state , crystallography , stereochemistry , atomic physics , quantum mechanics , catalysis , physics , organic chemistry , excited state
Cyclonona‐3,5,7‐trienylidene ( 1 ) changes from being a transition state (TS) to minimum states when substituted by α‐methyl groups and ά‐X, where X = CMe 2 , NMe, PMe, O, S, cyclopropyl, and SiMe 2 ( 2 , 3 , 4 , 5 , 6 , 7 , 8 , respectively) at density functional theory. Specifically, the parent carbene 1 exhibits a negative vibrational force constant and proves to be an unreachable electrophilic TS while shows C s symmetry with an NBO atomic charge of +0.70 on its carbenic center. It has a triplet ground state with a rather small singlet‐triplet energy gap (Δ E s–t = −4.1 kcal/mol). In contrast, all of its seven scrutinized derivatives enjoy reachable global minima, with C 1 symmetry, desired nucleophilicity, and singlet closed shell (S cs ) ground states (for all but 8 which remains triplet). Stability is indicated by relative Δ E s–t values: 2 > 3 > 4 > 5 > 6 > 7 > 1 > 8 . The highest Δ E s–t as well as NBO carbenic atomic negative charge (−0.74) are displayed by 2 . Our carbenes ( 2 , 3 , 4 , 5 , 6 , 7 ) appear more nucleophilic than the synthesized N ‐heterocyclic carbenes (imidazol‐2‐ylidenes). Copyright © 2013 John Wiley & Sons, Ltd.