Selective Hydrosilation of CO₂ to a Bis(silylacetal) Using an Anilido Bipyridyl‐Ligated Organoscandium Catalyst

Abstract

A rigid anilido bipyridyl ligand has been designed for use in an organoscandium-based carbon dioxide hydrosilation catalyst. Ligand attachment by alkane elimination results in metalation of an aryl CÀH bond in a 3,5-di-tertbutylphenyl group installed on the pyridyl unit, thus rendering the ligand tetradentate. Insertion of CO 2 into the newly formed Sc À C bond leads to a k 1 carboxylate which, when treated with the borane B(C 6 F 5 ) 3 , becomes hemilabile. In addition to activating the catalyst, the k 1 carboxylate effectively sequesters free B(C 6 F 5 ) 3 and the ensemble is able to effectively hydrosilate CO 2 , in the presence of excess Et 3 SiH, almost exclusively to R 3 SiOCH 2 OSiR 3 . A maximum turnover number of about 3400 (conversion of silane) is observed. Mechanistic experiments suggest that the sequestration of free B(C 6 F 5 ) 3 by the hemilabile carboxylate contributes to the selectivity observed and prevents over reduction to methane.Carbon dioxide (CO 2 ) is a cheap, readily available source of

Fifty Years of Hydrosilylation in Polymer Science: A Review of Current Trends of Low-Cost Transition-Metal and Metal-Free Catalysts, Non-Thermally Triggered Hydrosilylation Reactions, and Industrial Applications

“…Most commonly used and well-studied photo-initiatable catalysts are platinum-based ones such as a A novel method for obtaining α-silyl carbonyl products using B(C 6 F 5 ) 3 as catalyst was reported by Kim and Chang [69]. Unlike previously reported hydrosilylations of unsaturated polar bonds (such as carbonyls, imines, and nitriles [70][71][72]), the authors demonstrated the feasibility of the chemoselective α-silylation of conjugated esters and amides, in which the carbonyl group was left intact (Figure 29). According to preliminary mechanistic studies, the reaction proceeds in two steps, namely rapid 1,4-hydrosilylation of conjugated carbonyls and slow silyl group migration of a silyl ether intermediate.…”

Reducing CO2 to Methanol Using Frustrated Lewis Pairs: On the Mechanism of Phosphine–Borane-Mediated Hydroboration of CO2

“…3 Although most of the reported systems use heterogeneous catalysts, some homogeneous transition-metal based catalytic systems have been developed for the reduction of CO2 to formic acid, 4 formate, 5 formaldehyde, 6 methanol, 7 methane 8 and acetals. 9 Organocatalysts, as species not comprised of transition metals, are still scarce in the field of CO2 functionalization to valuable chemicals. 10 Notable systems include highly Lewis acidic aluminum species 11 and silyl cations 12 which have been shown to reduce CO2 with low selectivity to mixtures of products comprising methane, methanol and a number of alkylation byproducts.…”

Fe and Co Complexes of Rigidly Planar Phosphino-Quinoline-Pyridine Ligands for Catalytic Hydrosilylation and Dehydrogenative Silylation

“…A structurally related NNN ligand platform 8-amino-2-(pyrid-2′-yl)quinoline has been prepared and complexed to Sc. 26,27 Lithiation of 8-bromo-2-(pyrid-2′yl)quinoline with butyl lithium gave 8-lithio-2-(pyrid-2′yl)quinoline, which reacted readily with i Pr 2 PCl to give the corresponding tertiary phosphine iPr PQpy. Prepared analogously using (C 6 F 5 ) 2 PCl was the bis(pentafluorophenyl)phosphine derivative ArF PQpy (Scheme 1).…”