Related Experiment Video
Updated: Dec 1, 2025
Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
Partnering a Three-Coordinate Gallium Cation with a Hydroborate Counter-Ion for the Catalytic Hydrosilylation of CO2
Alexa Caise1, Jamie Hicks1, M Ángeles Fuentes1
1Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK.
Abstract:
A novel β-diketiminate stabilized gallium hydride, (Dipp L)Ga(Ad)H (where (Dipp L)={HC(MeCDippN)2 }, Dipp=2,6-diisopropylphenyl and Ad=1-adamantyl), has been synthesized and shown to undergo insertion of carbon dioxide into the Ga-H bond under mild conditions. In this case, treatment of the resulting κ1 -formate complex with triethylsilane does not lead to regeneration of the hydride precursor. However, when combined with B(C6 F5 )3 , (Dipp L)Ga(Ad)H catalyses the reductive hydrosilylation of CO2 . Under stoichiometric conditions, the addition of one equivalent of B(C6 F5 )3 to (Dipp L)Ga(Ad)H leads to the formation of a 3-coordinate cationic gallane complex, partnered with a hydroborate anion, [(Dipp L)Ga(Ad)][HB(C6 F5 )3 ]. This complex rapidly hydrometallates carbon dioxide and catalyses the selective reduction of CO2 to the formaldehyde oxidation level at 60 °C in the presence of Et3 SiH (yielding H2 C(OSiEt3 )2 ). When catalysis is undertaken in the presence of excess B(C6 F5 )3 , appreciable enhancement of activity is observed, with a corresponding reduction in selectivity: the product distribution includes H2 C(OSiEt3 )2 , CH4 and O(SiEt3 )2 . While this system represents proof-of-concept in CO2 hydrosilylation by a gallium hydride system, the TOF values obtained are relatively modest (max. 10 h-1 ). This is attributed to the strength of binding of the formatoborate anion to the gallium centre in the catalytic intermediate (Dipp L)Ga(Ad){OC(H)OB(C6 F5 )3 }, and the correspondingly slow rate of the turnover-limiting hydrosilylation step. In turn, this strength of binding can be related to the relatively high Lewis acidity measured for the [(Dipp L)Ga(Ad)]+ cation (AN=69.8).
More Related Videos
09:37Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
06:32A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions
Published on: August 17, 2016
Related Concept Videos
02:36Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
03:08Hydroboration-Oxidation of Alkenes
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
02:13Reduction of Alkenes: Catalytic Hydrogenation
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.