Homogeneous Catalytic Reduction of CO₂ with Silicon‐Hydrides, State of the Art

Abstract

During recent years, the catalytic transformation of CO 2 using silicon-hydrides as reductants has emerged as a promising methodology that allows the selective reduction of CO 2 to the formate, formaldehyde, methoxide or methane level under mild reaction conditions. Moreover, some catalysts have been employed for the formylation and/or methylation of the NÀH bonds of secondary and/or primary amines by their reaction with CO 2 and hydrosilanes. This work summarizes the different catalytic systems that have shown to be efficient for the abovementioned reactions. Furthermore, a brief description of the reactions performance and the conditions employed in each case is included.[a] Dr. ReviewsScheme 12. Complex RuÀS (21)-catalyzed CO 2 -reduction with HSiEt 3 to the bis(silyl)acetal level.Scheme 13. [Ni(PBP)]-catalyzed CO 2 -reduction with hydrosilanes to the bis (silyl)acetal level.Scheme 14. Reaction of [Sc(RCO 2 )(AbP t Bu 2 )] (26) with B(C 6 F 5 ) 3 . Ar= 3,5-ditertbutylphenyl, R=CH 2 SiMe 2 Ph.Scheme 15. CO 2 -reduction with HSiPh 3 to the bis(silyl)acetal level catalyzed by ion pairs 30 (0.5 mol % + 2.0 mol % of B(C 6 F 5 ) 3 ) and 31 (2.0 mol % + 8.0 mol % of B(C 6 F 5 ) 3 ).Scheme 16. CO 2 -reduction with HSiEt 3 to the bis(silyl)acetal level catalyzed by the N,P-heterocyclic germylene-B(C 6 F 5 ) 3 adduct (34).

Mechanistic Insights on the Functionalization of CO2 with Amines and Hydrosilanes Catalyzed by a Zwitterionic Iridium Carboxylate‐Functionalized Bis‐NHC Catalyst

“…The catalytic reaction of CO 2 with hydrosilanes has emerged as a thermodynamically favored procedure that allows for the reduction of CO 2 under mild reaction conditions . Nonetheless, this methodology faces lack of selectivity, as silylformates are usually obtained among other products, such as bis(silyl)acetals, methoxysilanes and methane, in variable relative amounts (Scheme ) .…”

Cyclic(Alkyl)(Amino)Carbene (CAAC)‐Supported Zn Alkyls: Synthesis, Structure and Reactivity in Hydrosilylation Catalysis

“…Metal‐catalyzed CO 2 hydrosilylation, preferably with cheap and non‐toxic organometallic compounds, is currently attracting considerable attention as an efficient route to CO 2 ‐derived small molecules with added value such as HCO 2 SiR 3 , R 3 SiOCH 2 OSiR 3 , MeOSiR 3 (formate, aldehyde and methanol equivalent, respectively) and CH 4 . Only a few Zn‐based catalysts for CO 2 functionalization have been developed . Cations 5 + and 7 + were tested as potential CO 2 functionalization catalysts.…”

“…[29] Only af ew Zn-based catalysts for CO 2 functionalization have been developed. [14,30] Cations 5 + + and 7 + + were tested as potentialC O 2 functionalization catalysts. CAAC-Zn cation 5 + + is unreactive towards CO 2 (1.5 atm) in the presence of HSiEt 3 under the studied conditions (5 mol %o f5 + + ,C 6 D 5 Br,9 08C,24 h).…”

Catalytic Conversion of Carbon Dioxide through C-N Bond Formation

“…For the past fifteen years, reductive methylation using N-site-based nucleophiles and CO 2 to give the corresponding methyl amines or formamide, which represents one of the most economical and environmentally friendly routes for C-N bond formation using CO 2 as C 1 building block has been investigated intensively. Recently, in this hot field, several groups such as Cantat (2015, reductive functionalization of CO 2 with amines) [111,112], Yan (2015, transition metal-catalyzed methylation) [113], Beller (2017, catalytic methylation) [114], He (2018, transition-metal-free catalysis) [115], Kühn (2018, an update of CO 2 catalytic conversion) [116], Fernández-Alvarez and Oro (2018, homogeneous catalytic reduction of CO 2 with silicon-hydrides) [117], Motokura (2018, organocatalysis with silanes) [118], have reviewed the recent developments in CO 2 hydrogenation based on amine substrates from different viewpoints. On the basis of the previous reviews and the integrity of this article, here, the introduction of the development of CO 2 conversion based on amines will be emphasized in a special view.…”