Efficient access to substituted silafluorenes by nickel-catalyzed reactions of biphenylenes with et2SiH2

Jens Michael Breunig, Puneet Gupta, Animesh Das, Samat Tussupbayev, Martin Diefenbach, Michael Bolte, Matthias Wagner, Max C. Holthausen, Hans Wolfram Lerner

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The reaction of biphenylene (1) with Et2SiH2 in the presence of [Ni-(PPhMe2)4] results in the formation of a mixture of 2-diethylhydrosilylbiphenyl [2(Et2HSi)] and 9,9,-diethyl-9-silafluorene (3). Silafluorene 3 was isolated in 37.5% and 2(Et2HSi) in 36.9% yield. The underlying reaction mechanism was elucidated by DFT calculations. 4-Methyl-9,9-diethyl-9-silafluorene (7) was obtained selectively from the [Ni(PPhMe2)4]-catalyzed reaction of Et2SiH2 and 1-methylbiphenylene. By contrast, no selectivity could be found in the Ni-catalyzed reaction between Et2SiH2 and the biphenylene derivative that bears tBu substituents in the 2- and 7-positions. Therefore, two pairs of isomers of tBu-substituted silafluorenes and of the related diethylhydrosilylbiphenyls were formed in this reaction. However, a subsequent dehydrogenation of the diethylhydrosilylbiphenyls with Wilkinson's catalyst yielded a mixture of 2,7-di-tert-butyl-9,9-di-ethyl-9-silafluorene (8) and 3,6-di-tert-butyl-9,9-diethyl-9-silafluorene (9). Silafluorenes 8 and 9 were separated by column chromatography.

Original languageEnglish (US)
Pages (from-to)3163-3173
Number of pages11
JournalChemistry - An Asian Journal
Issue number11
StatePublished - Sep 9 2014


  • C-C activation
  • Density functional calculations
  • Nickel
  • Si-H activation
  • Silanes


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