Carbodiimides as catalysts for the reduction of CO₂ with boranes

Abstract

Carbodiimides catalyse the reduction of CO2 with H-BBN or BH3·SMe2 to give either mixtures of CH2(OBBN)2 and CH3OBBN or (MeOBO)3 and B(OMe)3 under mild conditions (25-60 °C, 1 atm CO2). Stoichiometric reactions and theoretical calculations were performed to unveil the mechanism of these catalytic processes.

Alkyne 1,1‐Hydroboration to a Reactive Frustrated P/B‐H Lewis Pair

“…We notice that at this temperature there is only a single set of NMR resonances for the pair of p‐tolyl groups at the two nitrogen atoms. We interpret this observation as an indication for the rapid boryl migration between these two nitrogen centers [17a, 23] under these condition at the NMR time scale. A decoalscence was observed upon decreasing the temperature of the NMR measurements (the spectra are depicted in the Supporting Information).…”

From CO2 activation to catalytic reduction: a metal-free approach

“…In 2018, the viability of commercially available alkylic carbodiimides (CDIs) was demonstrated when they were treated with boranes such as 9-BBN or BH 3 in the catalytic hydroboration of CO 2 . 55 The catalytically-active FLP species were formed in situ via the reaction of CDIs with borane and CO 2 . The CDIs react with boron hydrides to form boron amidinates, 56 which have potential to act as an FLP owing to the presence of N/B combinations.…”

More Than Just a Reagent: The Rise of Renewable Organohydrides for Catalytic Reduction of Carbon Dioxide

“…Thus, it necessitates the FLP to generate more reactive hydrides for better catalytic activity. Hydroboration of CO 2 has been well studied using phosphine‐borane, [85–89,104] amine‐borane [90–93,104] FLPs as organocatalysts. Few boron hydrides [94–96,104] and aluminum hydrides [95] also reported as efficient catalysts for hydroboration of CO 2 .…”

“…Various non‐metallic hydride donors have been used to reduce CO 2 . Considering non‐metallic hydrides, various hydrosilanes, [26–83] hydroboranes, [85–96] ammonia borane (AB type), [6,97–100] showed great promise towards the reduction of CO 2 to highly reduced products such as formic acid (2e − ), formaldehyde (4e − ), methanol (6e − ) or even most reduced methane (8e − ) in the presence of appropriate catalysts. However, CO 2 reduction by these organohydrides are not catalytic.…”