N,P‐Heterocyclic Germylene/B(C₆F₅)₃ Adducts: A Lewis Pair with Multi‐reactive Sites

Abstract

An N,P-heterocyclic germylene/B(C F ) Lewis adduct 2 presenting multi-reactive sites (P/B Lewis pair, germylene, Ge=P π-bond) is reported. In contrast to classical frustrated Lewis pairs or divalent Group 14 element species, 2 is able to activate two small molecules simultaneously. Of particular interest, 2 reacts with silanes leading to the formation of original cationic germylenes 3, and can be used as a metal-free catalyst for selective CO -hydrosilylation to H C(OSiEt ) .

Diverse Catalytic Systems and Mechanistic Pathways for Hydrosilylative Reduction of CO2

“…Outer‐sphere hydride transfer that does not involve LA activation has also been discussed, mainly for CO 2 hydrogenation processes . In some main‐group catalyst systems, direct H − transfer from E−H to free or LA‐activated CO 2 has also been proposed …”

“…In 2018, Kato et al. reported that an N,P‐heterocyclic germylene/B(C 6 F 5 ) 3 Lewis pair ( 44 ) exhibited multisite reactivity and the ability to readily cleave a Si−H bond of hydrosilanes into a highly reactive cationic silylated germylenes and an anionic hydridodoborate pair . Such an ion pair can subsequently deliver the formal hydride and silylium ions to CO 2 two times to give the selective formation of the bis(silyl)acetal reduction product (Scheme ).…”

Partnering a Three‐Coordinate Gallium Cation with a Hydroborate Counter‐Ion for the Catalytic Hydrosilylation of CO2

“…The use of 2‐H to catalyse the hydrosilylation of CO 2 represents a relatively rare example of the use of a main group hydride as a catalyst for this process [57, 58, 68] . That this system can be used to selectively generate (Et 3 SiO) 2 CH 2 , a potential source of formaldehyde, led us to investigate how this transformation proceeds.…”

“…Thus, a variety of homogenous catalytic systems based on metals (Pd/Pt, [14–17] Rh, [18] Re, [19, 20] Ru, [21–26] Ir, [8, 27–30] Co, [13, 31] Mn, [12] Zr, [32, 33] Cu, [34–38] Ni, [39–42] Sc, [43–46] Zn, [47–57] Mg [57, 58] and Sr [59] ), Lewis acids, [60–66] frustrated Lewis pairs (FLPs), [67, 68] organo‐catalysts, [69–75] alkali metal carbonates, [76, 77] and metal borohydrides [78] have been investigated for this process. Many of these catalytic systems feature reactive metal hydride or alkyl groups, which effect the initial activation of CO 2 via insertion.…”

“…Hence, controlling the quantity of B(C 6 F 5 ) 3 available for activation of the silane (to form the reactive species [R 3 Si‐H⋅⋅⋅B(C 6 F 5 ) 3 ]) is the subject of increasing study [43] . This can be effected through the use of either sub‐stoichiometric B(C 6 F 5 ) 3 , [32] or by using catalytic systems which sequester B(C 6 F 5 ) 3 during turnover, thereby inhibiting the formation of the activated silane in quantities sufficient to reduce the bis(silyl)acetal species further [20, 39, 44, 68] …”