Adamantyl compounds adduct

The fact that NHCs form stable compounds with beryllium, one of the hardest Lewis acids known and without p-electrons to back donate, shows the nu-cleophilicity of these ligands. Reaction of l,3-dimethylimidazolin-2-ylidene with polymeric BeCl2 results in the formation of the neutral 2 1 adduct 23 or the cationic 3 1 adduct 24. The first NHC-alkaline earth metal complex to be isolated was the 1 1 adduct 25 with MgEt2- Whereas l,3-dimesitylimidazolin-2-ylidene results in the formation of a dimeric compound, the application of sterically more demanding l,3-(l-adamantyl)imidazolin-2-ylidene gives a monomeric adduct. ... 

A series of moderately stable 2-siloxetanes has been prepared recently by irradiation of tris(trimethylsilyl)acylsilanes in the presence of a nonenolizable carbonyl compound110. The 2 + 2 cycloaddition is a dark process, since addition of the carbonyl compound to a preformed silene in the dark works equally well. The 2 + 2 adduct of benzophenone to 2-(l-adamantyl)-2-trimethylsiloxy-l,l-bis(trimethylsilyl)silene (42) was characterized by X-ray analysis. 

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