Abstract:The reaction of an NHC-stabilized silole silylene (1, 1-silacyclopentadienylidene) with one equivalent of internal acetylenes resulted in the formation of NHC-stabilized 1-silabicyclo[3.2.0]hepta-1,3,6-trienes, which subsequently reacted with one equivalent of the acetylene to yield an aryl-substituted 1,1'-spirobisilole (SBS). The SBSs can also be prepared by reaction of the NHC-stabilized silole silylene 1 with two equivalents of the acetylenes in good yields. The electronic structures of these SBSs have been studied by UV/Vis and emissionspectroscopy,asw ell as DFT calculations.

Summary of main observation and conclusion N‐Heterocyclic carbene (NHC) enabled the highly efficient catalytic hydroboration of a wide range of ketones and aldehydes under mild conditions, and a new mechanism of catalytic hydroboration reaction which involves direct hydride transfer is proposed.

The 1-hydro-1-lithio-silafluorene anion 2 has been isolated and characterized by single-crystal X-ray analysis for the first time. Three tetrahydrofuran molecules coordinate with lithium atoms in the crystal structure of 2. 2 was reacted with a number of electrophilic reagents and it can be used as a useful reagent for generating various functional hydrogen-substituted silafluorenes. Treatment of 2 with 2 equiv. of chlorobis(isopropyl)phosphine afforded chloro-substituted silafluorene 4. The reaction of 8 which has a SiH-SiBr fragment with IiPrMe (IiPr: 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene) led to the formation of an Si-Si bond cleavage product, NHC-stabilized silacyclopentadienylidene 9.

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