N-Heterocyclic carbene-catalyzed dehydration of α,ω-disilanol oligomers

Early/Late Heterobimetallic Tantalum/Rhodium Species Assembled Through a Novel Bifunctional NHC‐OH Ligand

“…Compound 2 sublimes (10 −5 mbar, 120 °C), which is in agreement with its neutral formulation, but is more easily purified by recrystallisation in THF. Although the activation of hydroxy groups by NHCs is suspected to be involved in several organocatalytic processes, little is known about the exact nature of the alcohol–NHC interaction and systematic experimental investigations are still lacking. This prompted us to explore in detail the structure of this unusual compound by NMR and IR spectroscopy as well as by XRD.…”

N‐Heterocyclic carbenes for metal‐free polymerization catalysis: an update

“…A more unusual example for NHC polymerization catalysis was provided by Baceiredo and co‐workers in 2008 and was focused on the polycondensation of α , ω ‐ disilanols . Despite water being released during this process, the NHCs did retain their activity over a long time, thus enabling the build‐up of considerable molecular weights (50 000–300 000 g mol −1 ).…”

N‐Heterocyclic Carbene Mediated Activation of Tetravalent Silicon Compounds: A Critical Evaluation

“…[26] Alternatively, the poor activity of 1 a may be due to differences in basicity compared with 1 b and 1 c. [39] It is also apparent that the subsequent polymerisation of silicone oligomer produced by ring opening of 14 could be catalysed by NHCs through hydrogen bonding to the corresponding silanol. [11] Scheme 9. NHC-mediated formation of azolium intermediates.…”

“…NHCs have been reported as catalysts or initiators of a wide variety of organic transformations that involve silicon compounds, including the cyanosilylation of aldehydes, ketones and imines,4 the trifluoromethylsilylation of aldehydes and ketones,5 Mukaiyama aldol reactions6 and aziridine addition reactions7 (Scheme ). They have also been proposed to facilitate σ‐bond metathesis between silanes and copper alkoxides,8 promote the group‐transfer polymerisation of acrylate monomers in the present of silyl ketene acetal initiators,9 facilitate ring‐opening polymerisation of cyclic siloxanes,10 catalyse the dehydration of disilanol oligomers11 and facilitate the reduction of CO 2 by hydrosilanes 12. This minireview will summarise the developments in this area, highlighting the mechanistic scenarios proposed and ending with a detailed discussion of the current knowledge regarding the role of Lewis acid–base NHC–Si interactions in the mechanistic course of these reactions.…”