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C( sp n )−X (n=1–3) Bond Activation by Palladium
Author(s) -
Hansen Thomas,
Sun Xiaobo,
Dalla Tiezza Marco,
Zeist WillemJan,
Poater Jordi,
Hamlin Trevor A.,
Bickelhaupt F. M.
Publication year - 2022
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.202103953
Subject(s) - palladium , catalysis , chemistry , steric effects , crystallography , substrate (aquarium) , density functional theory , ligand (biochemistry) , activation energy , oxidative addition , decomposition , atom (system on chip) , stereochemistry , computational chemistry , organic chemistry , computer science , embedded system , geology , biochemistry , oceanography , receptor
We have studied the palladium‐mediated activation of C( sp n )−X bonds (n = 1–3 and X = H, CH 3 , Cl) in archetypal model substrates H 3 C−CH 2 −X, H 2 C=CH−X and HC≡C−X by catalysts PdL n with L n = no ligand, Cl − , and (PH 3 ) 2 , using relativistic density functional theory at ZORA‐BLYP/TZ2P. The oxidative addition barrier decreases along this series, even though the strength of the bonds increases going from C( sp 3 )−X, to C( sp 2 )−X, to C( sp )−X. Activation strain and matching energy decomposition analyses reveal that the decreased oxidative addition barrier going from sp 3 , to sp 2 , to sp , originates from a reduction in the destabilizing steric (Pauli) repulsion between catalyst and substrate. This is the direct consequence of the decreasing coordination number of the carbon atom in C( sp n )−X, which goes from four, to three, to two along this series. The associated net stabilization of the catalyst–substrate interaction dominates the trend in strain energy which indeed becomes more destabilizing along this same series as the bond becomes stronger from C( sp 3 )−X to C( sp )−X.