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Updated: Jan 23, 2026

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Published on: July 30, 2017
Isolation of an N-Heterocyclic Carbene Complex of a Borasilene
Daniel Franz1, Tibor Szilvási2, Alexander Pöthig1
1Department of Chemistry, Catalysis Research Center and Institute of Silicon Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85748, Garching bei München, Germany.
Abstract:
Borasilenes, that is complexes which contain a boron-silicon double bond, have scarcely been isolated to date. In pursuit of such species, (Me3 Si)3 SiB(Cl)NHI (2, NHI=bulky N-heterocyclic imine) was prepared and treated with KOtBu to achieve formal extrusion of ClSiMe3 . The formation of an elusive borasilene (3int ) is postulated and it was verified by isolation of the N-heterocyclic carbene adduct (Me3 Si)2 SiB(I )NHI (4, I =1,3,4,5-tetramethyl-imidazolin-2-ylidene). X-ray crystallographic study and theoretical calculations on 4 diagnosed a boron-silicon double bond with marked zwitterionic character. The negative charge resides at the Si atom which marks the apex of a trigonal pyramid. Structural comparison of 4 with boron cation congeners (5+ , 6+ ) suggests that the positive charge is mainly located at the trigonal planar-coordinated B center. The conversion of 4 with pinacolborane (HBpin, 2 equiv) resulted in cleavage of the double bond to produce (Me3 Si)2 Si(Bpin)2 and (NHI)BH2 (I ).
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