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.

Evidence of a Donor–Acceptor (Ir–H)→SiR3Interaction in a Trapped Ir(III) Silane Catalytic Intermediate

“…23 These results indicate that the ion pairings in the latter BArF 24 − and BF 4 − salts are not largely different in a solvent of moderate polarity such as d 5 -PhCl and that ion-pair dissociation is only slightly enhanced in a more polar solvent such as CD 2 Cl 2 because the values of the D cation /D anion ratio remain close to 1. Static DFT calculations of idealized ion pair dissociation enthalpies 24 26 suggest that the slightly more favored dissociation of BArF 24 − should be entropy grounded in comparison to BF 4 − (Figure 2). If one considers the total cation−anion interaction energy ΔE int as defined by the energy decomposition analysis 27 [BArF 24 ] − .…”

Consistent structures and interactions by density functional theory with small atomic orbital basis sets

“…They are evaluated "plain" without any correction because they are still used in this form in many applications. Although B3LYP can be improved by adding D3 and gCP corrections 50 and M06-2X through the D3(zero-damping) scheme, 51,52 we think that a comparison to the plain functionals also provides insight how large dispersion and BSSE effects (and their mutual compensation) are in typical systems. A separate and detailed analysis of these effects is, however, beyond the scope of the present study which focuses on the new approach.…”

Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

“…Final reported energies are M06L/ TZVP * SDD//B3LYP/SVP * SDD electronic energies corrected with ZPEs, thermal energies and entropy effects calculated at 298 K using the B3LYP/6-31G(d) * SDD method. The results include dispersion, despite not incorporating long-range dispersion interactions [37]. We also corrected the energy for solvation effects present in an acetone solution that were calculated at the M06L/6-311G(d, p) * SDD//B3LYP/6-31G(d) * SDD level with the PCM method.…”