Counterion Effect in Cobaltate‐Catalyzed Alkene Hydrogenation

Abstract

We show that countercations exert a remarkable influence on the ability of anionic cobaltate salts to catalyze challenging alkene hydrogenations. An evaluation of the catalytic properties of [Cat][Co(η4‑cod)2] (Cat = K (1), Na (2), Li (3), (Depnacnac)Mg (4), and N(nBu)4 (5); cod = 1,5‑cyclooctadiene, Depnacnac = {2,6‑Et2–C6H3–N=C(CH3)}2C)]) demonstrated that the lithium salt 3 and magnesium salt 4 drastically outperform the other catalysts. Complex 4 gave the most active catalyst, which readily promotes the hydrogenation of highly congested alkenes under mild conditions. A plausible catalytic mechanism is proposed based on density functional theory (DFT) investigations. Furthermore, combined molecular dynamics (MD) simulation and DFT studies were used to examine the turnover‑limiting migratory insertion step. These results suggest an active co‐catalytic role of the counterion in the hydrogenation reaction through the coordination to cobalt hydride intermediates.

Non-coordinating counteranion as a powerful tool to tune the activity of copper water oxidation catalysts

“…Despite it has been recognized that non-coordinating counteranions are important for metal complexes in many catalytic processes, 18–20 few studies described the influence of non-coordinating counteranions on the catalytic activity of Cu-WOCs. In this work, we synthesized two types of copper-bipyridine complexes, [(bpyR)Cu]X, with five different counteranions (R = H or CH 3 ; X = OAc − , Cl − , SO 4 2− , NO 3 − , OTf − ) as shown in Scheme 1 and Fig.…”

“…According to previous studies, the catalytic reactions can be accelerated by tuning the coordinating ability or changing the p K b of counteranions. 20 Hence, we analyze the relationship between TOF and the coordinating ability index a ™ as well as TOF and p K b . Fig.…”