title: The thermochemistry of london dispersion-driven transition metal reactions: getting the 'right answer for the right reason'.
abstract: Reliable thermochemical measurements and theoretical predictions for reactions involving large transition metal complexes in which long-range intramolecular London dispersion interactions contribute significantly to their stabilization are still a challenge, particularly for reactions in solution. As an illustrative and chemically important example, two reactions are investigated where a large dipalladium complex is quenched by bulky phosphane ligands (triphenylphosphane and tricyclohexylphosphane). Reaction enthalpies and Gibbs free energies were measured by isotherm titration calorimetry (ITC) and theoretically 'back-corrected' to yield 0 K gas-phase reaction energies (ΔE). It is shown that the Gibbs free solvation energy calculated with continuum models represents the largest source of error in theoretical thermochemistry protocols. The ('back-corrected') experimental reaction energies were used to benchmark (dispersion-corrected) density functional and wave function theory methods. Particularly, we investigated whether the atom-pairwise D3 dispersion correction is also accurate for transition metal chemistry, and how accurately recently developed local coupled-cluster methods describe the important long-range electron correlation contributions. Both, modern dispersion-corrected density functions (e.g., PW6B95-D3(BJ) or B3LYP-NL), as well as the now possible DLPNO-CCSD(T) calculations, are within the 'experimental' gas phase reference value. The remaining uncertainties of 2-3 kcal mol(-1) can be essentially attributed to the solvation models. Hence, the future for accurate theoretical thermochemistry of large transition metal reactions in solution is very promising.
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institute of Physical & Theoretical Chemistry, University of Bonn Beringstr. 4-6, 53115 Bonn (Germany) E-mail: grimme@thch.uni-bonn.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hansen
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institute of Physical & Theoretical Chemistry, University of Bonn Beringstr. 4-6, 53115 Bonn (Germany) E-mail: grimme@thch.uni-bonn.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bannwarth
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institute of Physical & Theoretical Chemistry, University of Bonn Beringstr. 4-6, 53115 Bonn (Germany) E-mail: grimme@thch.uni-bonn.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.affiliation: Strasbourg Institute of Chemistry, CNRS, UMR 7177, Laboratory of Chemistry & Organometallic Systems, University of Strasbourg 4 rue Blaise Pascal, 67000 Strasbourg (France) E-mail: djukic@unistra.fr.
authors.forename: Predrag
authors.initials: P
authors.lastname: Petrović
authors.affiliation: Strasbourg Institute of Chemistry, CNRS, UMR 7177, Laboratory of Chemistry & Organometallic Systems, University of Strasbourg 4 rue Blaise Pascal, 67000 Strasbourg (France) E-mail: djukic@unistra.fr.
authors.forename: Christophe
authors.initials: C
authors.lastname: Werlé
authors.affiliation: Strasbourg Institute of Chemistry, CNRS, UMR 7177, Laboratory of Chemistry & Organometallic Systems, University of Strasbourg 4 rue Blaise Pascal, 67000 Strasbourg (France) E-mail: djukic@unistra.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Djukic
keywords: London dispersion interactions; density functional theory; isothermal titration calorimetry; local coupled cluster; transition metal reactions