A Cationic Zinc Hydride Cluster Stabilized by an N‐Heterocyclic Carbene: Synthesis, Reactivity, and Hydrosilylation Catalysis

Abstract

The trinuclear cationic zinc hydride cluster [(IMes)3Zn3H4(THF)](BPh4)2 (1) was obtained either by protonation of the neutral zinc dihydride [(IMes)ZnH2]2 with a Brønsted acid or by addition of the putative zinc dication [(IMes)Zn(THF)](2+). A triply bridged thiophenolato complex 2 was formed upon oxidation of 1 with PhS-SPh. Protonolysis of 1 by methanol or water gave the corresponding trinuclear dicationic derivatives. At ambient temperature, 1 catalyzed the hydrosilylation of aldehydes, ketones, and nitriles. Carbon dioxide was also hydrosilylated under forcing conditions when using (EtO)3SiH, giving silylformate as the main product.

Selective Metal‐Free Hydrosilylation of CO2 Catalyzed by Triphenylborane in Highly Polar, Aprotic Solvents

“…While investigating zinc hydrides and their reactivity towards CO 2 , we discovered that triphenylborane (BPh 3 ) is also capable of effecting this transformation. The groups of Piers and Gevorgyan have described the more strongly Lewis acidic B(C 6 F 5 ) 3 as a versatile catalyst for addition of Si−H moieties across C=O, C=N, and C=C bonds.…”

Reduction of carbon dioxide and organic carbonyls by hydrosilanes catalysed by the perrhenate anion

“…[1][2][3] A variety of catalysts have been discovered and developed for this reaction, including complexes of Co, 4 Cu, [5][6][7][8] Ir, [9][10][11][12][13][14] Ni, [15][16][17] Pd/Pt, 18 Rh, 19 Ru, [20][21][22][23][24][25] Sc, 26 Zn, [27][28][29] and Zr, 30 frustrated Lewis pairs, [31][32][33][34][35][36] organocatalysts, [37][38][39][40][41][42] alkali metal carbonates, 43 and even polar solvents such as DMF. 38 These reactions result in various reduction products including silyl-formates, -acetals, andethers, CO, and methane.…”

Efficient CO2 Insertion and Reduction Catalyzed by a Terminal Zinc Hydride Complex

“…[3] Thecatalytic reduction of CO 2 with silanes is well-known, mainly using ruthenium complexes with ac ombination of high CO 2 pressures (20-80 bar) and moderate to high temperatures (45-100 8 8C), [4] but also Cu, [5] Ir, [6] and Pd [7] complexes were found to catalyze this reaction under mild conditions.In terms of price,a bundance,a nd toxicity of the metal center, the use of zinc-based systems is of significant interest. [8][9][10][11][12] However,these systems require either high temperatures and high pressures or only show low to moderate turnover numbers and turnover frequencies.O nly the recently introduced [Tism PriBenz ]b ased system was found to catalyze the hydrosilylation of CO 2 under ambient conditions,albeit with the use of ab orane additive and with only low turnover frequencies. [8][9][10][11][12] However,these systems require either high temperatures and high pressures or only show low to moderate turnover numbers and turnover frequencies.O nly the recently introduced [Tism PriBenz ]b ased system was found to catalyze the hydrosilylation of CO 2 under ambient conditions,albeit with the use of ab orane additive and with only low turnover frequencies.…”

“…Indeed, we found [Tntm]ZnH to catalytically reduce CO 2 with trimethoxysilane at room temperature and under mild conditions.T his is the first zinc-based system capable of catalytically reducing CO 2 at room temperature without the need of any additive and is also the most active system up to date.T he intermediate formate complex [Tntm]Zn(O 2 CH) was isolated and fully characterized. [8][9][10][11][12] [Tntm]ZnH (2)was prepared by reaction of the respective zinc trimethylsilanolate complex [Tntm]Zn(OSiMe 3 )(1)with aslight excess of (MeO) 3 SiH in THF in 85 %yield, similar to apreviously described method. Reported zinc-based catalysts for the hydrosilylation of CO 2 .…”