Iron Catalysts with Silyl-NHC Chelate Ligands: Controlling Factors for Hydroboration vs. Dehydrogenative Borylation
Nozomu Ishiwata1, Takashi Komuro1, Kasumi Takahashi1
1Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki Aza-Aoba, Aoba-ku, Sendai, 980-8578, Japan.
Abstract:
Various iron complexes 1, featuring silyl-NHC chelate ligands (NHC = N-heterocyclic carbene) were synthesized and investigated for their catalytic performance in the borylation reactions of olefins. Complexes 1 facilitated both hydroboration and dehydrogenative borylation of olefins with HBpin, yielding borylalkanes and borylalkenes, respectively. The selectivity between the two pathways was found to be governed by the steric effect of a substituent on one nitrogen atom of the NHC moiety. Possible catalytic mechanisms including hydroborato and β-agostic-alkyl complexes as potential resting states or intermediates are proposed based on stoichiometric reactions.
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