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The Thermochemistry of Alkyne Insertion into a Palladacycle Outlines the Solvation Conundrum in DFT
Author(s) -
Milovanović Milan R.,
Boucher Mélanie,
Cornaton Yann,
Zarić Snežana D.,
Pfeffer Michel,
Djukic JeanPierre
Publication year - 2021
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202100750
Subject(s) - thermochemistry , chemistry , solvation , alkyne , standard enthalpy of formation , insertion reaction , isothermal titration calorimetry , chlorobenzene , computational chemistry , pericyclic reaction , organic chemistry , molecule , catalysis
In an effort to determine the thermochemistry of established organometallic transformation, the well documented reaction of alkynes with a palladacycle was investigated by isothermal titration calorimetry (ITC). Although the mechanism of the insertion of unsaturated substrates into the Pd−C bond of cyclopalladated compounds is known, no information is available so far about their thermochemistry. The enthalpies of the reactions of Ph−C≡C−Ph and MeOC(O)−C≡C(O)COMe with the bisacetonitrilo salt of the N,N ‐benzylamine palladacycle were determined by ITC in chlorobenzene after having optimized the conditions to ensure that only the double and a single insertion of alkynes were occurring respectively. The reaction energy profile established by DFT for the double insertion process involving Ph−C≡C−Ph confirmed earlier conclusions on the rate determining character of the first insertion. Further computations of reaction enthalpies reveal significant discrepancies between ITC and DFT‐D/continuum solvation enthalpies, that are suspected to arise from an unexpected explicit noncovalent interaction of PhCl with the components of the reaction.