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Stabilization of Linear C 3 by Two Donor Ligands: A Theoretical Study of L‐C 3 ‐L (L=PPh 3 , NHC Me , cAAC Me ) **
Author(s) -
Gorantla Sai Manoj N. V. T.,
Pan Sudip,
Mondal Kartik Chandra,
Frenking Gernot
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003064
Subject(s) - carbene , cumulene , chemistry , adduct , bond dissociation energy , moiety , crystallography , phosphine , dissociation (chemistry) , ab initio quantum chemistry methods , stereochemistry , molecule , ab initio , density functional theory , bond length , computational chemistry , crystal structure , biochemistry , organic chemistry , catalysis
Quantum chemical studies using density functional theory and ab initio methods have been carried out for the molecules L‐C 3 ‐L with L=PPh 3 ( 1 ), NHC Me ( 2 , NHC=N‐heterocyclic carbene), and cAAC Me ( 3 , cAAC=cyclic (alkyl)(amino) carbene). The calculations predict that 1 and 2 have equilibrium geometries where the ligands are bonded with rather acute bonding angles at the linear C 3 moiety. The phosphine adduct 1 has a synclinal ( gauche ) conformation whereas 2 exhibits a trans conformation of the ligands. In contrast, the compound 3 possesses a nearly linear arrangement of the carbene ligands at the C 3 fragment. The bond dissociation energies of the ligands have the order 1 < 2 < 3 . The bonding analysis using charge and energy decomposition methods suggests that 3 is best described as a cumulene with electron‐sharing double bonds between neutral fragments (cAAC Me ) 2 and C 3 in the respective electronic quintet state yielding (cAAC Me )=C 3 =(cAAC Me ). In contrast, 1 and 2 possess electron‐sharing and dative bonds between positively charged ligands [(PPh 3 ) 2 ] + or [(NHC Me ) 2 ] + and negatively charged [C 3 ] − fragments in the respective doublet state.