A recent study showed that a Mn-pincer could catalyze the acceptorless dehydrogenative coupling of nitriles and alco-hols to yield acrylonitriles. The reaction mechanism pro-posed in that work contained some intermediates that, in most of the cases, were not characterized. Moreover, one of the intermediates involved a charged separation, which is unlikely in apolar solvents. To clarify the reaction mecha-nism of this critical reaction, we decided to perform a DFT study. Our results prove the existence of a cooperative effect of the metal and the ligand in several steps of the catalytic cycle. We also find the presence of several equilib-ria between isomeric intermediates where water, or the same alcohol reagent, take part in assisting the proton trans-fer. Furthermore, we have analyzed the charge separated structure proposed experimentally and have found a nearly pure covalent bond between the two expected charged moieties. Finally, the Knoevenagel condensation step that generates the acrylonitrile is found to be the rate-determining step.

New highly nucleophilic homogeneous and heterogeneous catalysts based on the 3,4-diaminopyridine scaffold are reported for the halogen-free cycloaddition of CO ₂ to epoxides.

Density functional theory calculations have been used to investigate the activation mechanism for the precatalyst series [Pd]-X-1–4 derived from [Pd(IPr)(R-allyl)X] species by substitutions at the terminal position of the allyl moiety ([Pd] = Pd(IPr); R = H (1), Me (2), gem-Me₂ (3), Ph (4), X = Cl, Br). Next, we have investigated the Suzuki–Miyaura cross-coupling reaction for the active catalyst species IPr-Pd(0) using 4-chlorotoluene and phenylboronic acid as substrates and isopropyl alcohol as a solvent. Our theoretical findings predict an upper barrier trend, corresponding to the activation mechanism for the [Pd]-Cl-1–4 series, in good agreement with the experiments. They indeed provide a quantitative explanation of the low yield (12%) displayed by [Pd]-Cl-1 species (ΔG^⧧ ≈ 30.0 kcal/mol) and of the high yields (≈90%) observed in the case of [Pd]-Cl-2–4 complexes (ΔG^⧧ ≈ 20.0 kcal/mol). Additionally, the studied Suzuki–Miyaura reaction involving the IPr-Pd(0) species is calculated to be thermodynamically favorable and kinetically facile. Similar investigations for the [Pd]-Br-1–4 series, derived from [Pd(IPr)(R-allyl)Br], indicate that the oxidative addition step for IPr-Pd(0)-mediated catalysis with 4-bromotoluene is kinetically more favored than that with 4-chlorotoluene. Finally, we have explored the potential of Ni-based complexes [Ni((IPr)(R-allyl)X] (X = Cl, Br) as Suzuki–Miyaura reaction catalysts. Apart from a less endergonic reaction energy profile for both precatalyst activation and catalytic cycle, a steep increase in the predicted upper energy barriers (by 2.0–15.0 kcal/mol) is calculated in the activation mechanism for the [Ni]-X-1–4 series compared to the [Pd]-X-1–4 series. Overall, these results suggest that Ni-based precatalysts are expected to be less active than the Pd-based precatalysts for the studied Suzuki–Miyaura reaction.