Neutral, Cationic and Hydride‐substituted Siloxygermylenes

Abstract

The introduction of the labile trimethylsiloxy group to Ge centers in the presence of an N-heterocyclic carbene donor is reported. The new complex IPr⋅GeCl(OSiMe ) (IPr=[(HCNDipp) C:]; Dipp=2,6-iPr C H ) was readily converted into the structurally unique Ge siloxy(hydrido)germylene IPr⋅GeH(OSiMe )⋅BH by treatment with lithium borohydride. Additionally, the reactive siloxygermylene cation [IPr⋅Ge(OSiMe )] was synthesized and clean oxidative addition of CH Cl was demonstrated. The two-coordinate [IPr⋅Ge(OSiMe )] cation also promoted the catalytic hydroborylation of sterically hindered ketones under mild conditions, with enhanced reactivity stemming from an open coordination site at Ge.

The key role of R–NHC coupling (R = C, H, heteroatom) and M–NHC bond cleavage in the evolution of M/NHC complexes and formation of catalytically active species

“…In these reactions, heteroatom reagents are thought to act as Lewis acids. Transformations of M–NHC to B–NHC bonds have been reported for Li/NHC, 108 Fe II /NHC 137 and Ge II /NHC 122 complexes ( Table 1 column 4). For example, reaction between Ge II /NHC complex 40 and LiBH 4 in Et 2 O affords NHC–BH 3 adduct 41 ( Scheme 9 ).…”

“…For example, reaction between Ge II /NHC complex 40 and LiBH 4 in Et 2 O affords NHC–BH 3 adduct 41 ( Scheme 9 ). 122 Reaction of complex 42 with Me 3 SiCl affords compound 43 ( Scheme 9 ). 108 A similar adduct was detected by NMR in a C 6 D 6 solution of [Pd(I t Bu) 2 ] complex and Me 3 SiI after 40 day storage at room temperature; 175 the authors suggested that the NHC–SiMe 3 adduct was formed via Pd–NHC dissociation and subsequent reaction of the free NHC with Me 3 SiI.…”

Heavier Tetrylenes as Single Site Catalysts

“…The first example of Ge(II) cation catalyzed hydroboration was reported by Rivard and coworkers. [77] They have synthesized a siloxygermylene cation [IPr•Ge(OSiMe 3 )][BAr 4 F ] (33) (Scheme 31) and utilized it for the hydroboration of sterically crowded benzophenone and electron-rich pinacolone. The conversion was done under mild conditions with quantitative yields.…”

Homoleptic Zinc‐Catalyzed Hydroboration of Aldehydes and Ketones in the Presence of HBpin

“…In contrast to hydroboration, the hydrosilylation of carbonyl compounds has been explored more . There are reports of a wide variety of metal catalysts from main group elements, including catalysts based on alkali or alkaline earth metals, namely, Al, Si, Ge, Sn, as well as rare earth metal catalysts such as those based on La and Yb, which have been used in the hydroboration of carbonyl compounds (Figure ). Transition metals such as Ti, Mn, Fe, Mo, Rh, Ru, Co, and Cu have also been used as the bases for developing catalysts.…”