Catalytic exploration of NHC–Ag(i)HMDS complexes for the hydroboration and hydrosilylation of carbonyl compounds

Abstract

The synthesis and full characterisation of two silver(I) amido complexes, stabilised by ancillary N-heterocyclic carbene (NHC) ligands is presented. The light stable complexes [Ag(IDipp)HMDS] 3 and [Ag(IAd)HMDS] 4 were explored...

Synthesis of N-heterocyclic carbene (NHC)-Au/Ag/Cu benzotriazolyl complexes and their catalytic activity in propargylamide cycloisomerization and carbonyl hydrosilylation reactions

“…It is worth mentioning that, compared to Ag-based CMAs, the applications of Cu-based CMA complexes in the hydrosilylation of carbonyl compounds are rare in the literature, and, therefore, these results showcase the potential of more sustainable systems for the synthesis industrially interesting silyl ethers. 26,31,33 On the other hand, complex 2a was inactive under these reaction conditions, underlining the necessity of the 1 H -benzotriazolyl anion in the complex scaffold (Table 2, entry 12). A wide range of aldehydes and ketones were then tested, using mainly catalysts 5a and 6a (Scheme 4).…”

“…Notably, all the experiments were set up and performed outside of a glovebox, as the CMA catalysts are air and moisture stable, in contrast to other literature works using catalysts that require special handling. 26,31,33 Solvent screening revealed that DCE was the most suitable choice for this reaction (entries 2–4). Moreover, time control experiments showed that only 1 hour, instead of 16, is long enough to achieve the formation of the cyclized product 8a in excellent yields (entry 5).…”

“…More recently, the same group has synthesized two additional Ag( i ) amido complexes, stabilized by ancillary N-heterocyclic carbene (NHC) ligands, and used them in hydroboration and hydrosilylation reactions (Scheme 1c). 33 It was thus shown that upon changing the Lewis donor from PCy 3 to a more electron donating NHC ligand, such as IPr [N,N′-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene] or IAd [N,N′-bis-(1-adamantyl)imidazol-2-ylidene], improved catalytic efficiency and conversion in the hydroboration and hydrosilylation of carbonyl compounds is observed.…”

π-Bonding of Group 11 Metals to a Tantalum Alkylidyne Alkyl Complex Promotes Unusual Tautomerism to Bis-alkylidene and CO2 to Ketenyl Transformation

“…Consequently, the C NHC signal in 3-Ag appears as a doublet of doublets at 190.59 ppm ( 1 J Ag−C = 145.4 and 167.0 Hz for 107 Ag and 109 Ag, respectively, see Figure 4f), in agreement with the literature. 93,103 The neopentylidene signal in 3-Ag is observed as a broad doublet, displaying a coupling constant of 30.3 Hz with silver (Figure 4f). These observations confirm the interaction of silver with the NHC and both neopentylidene moieties in 3-Ag on the NMR time scale.…”

%VBur index and steric maps: from predictive catalysis to machine learning

“…There are different reasons, either because it blocks a coordination of an additional ligand, because it leaves the perfect cavity in the first coordination sphere around the metal to interact with the substrates, and actually, it is common then that the most sterically protected metal centre is the most effective catalytically. 237,238…”