Synthesis and Study of Janus Bis(carbene)s and Their Transition‐Metal Complexes

Abstract

Deuces wild: From catalysis through materials science to biology, N‐heterocyclic carbenes (NHCs) can truly be regarded as a wild card of ligands. A new series of “two‐faced” (Janus‐type) ligands composed of two linearly opposed NHCs fused to an arene linker has been synthesized and can be used to prepare discrete bimetallic complexes.

Synthesis and Study of 5,5′‐Bibenzimidazolylidenes and Their Bimetallic Complexes

“…These observations were supported by the crystal structures of one of the 5,5Ј-bibenzimidazolium salts and its bis(carbene) derivative, which revealed relatively large dihedral angles of 51.2°and 47.8°, respectively, between the two aryl systems. We recently reported [8] a new class of benzobisimidazolylidenes (1) that feature two linearly opposed NHCs annulated to a common arene backbone. [9,10] These ditopic ligands proved to be instrumental in the preparation of new classes of bimetallic complexes [11] as well as polymeric [12] and self-assembled [13] materials.…”

“…[9,10] These ditopic ligands proved to be instrumental in the preparation of new classes of bimetallic complexes [11] as well as polymeric [12] and self-assembled [13] materials. Bis(NHC)s 1 are generally prepared by deprotonation of their respective benzobisimidazolium (BBI) salts, [8] with two strategies available for the syntheses of these precursors. In the first method, formylative cyclization of 1,2,4,5-tetraaminobenzene followed by alkylation affords a tetraalkylated BBI salt.…”

Probing the potential of N-heterocyclic carbenes in molecular electronics: redox-active metal centers interlinked by a rigid ditopic carbene ligand

“…9 A high degree of intermetallic coupling is pivotal for addressing the different states and is typically achieved by rigid, p-conjugated spacer ligands. The dicarbene A, derived from the corresponding diimidazolium salt (Scheme 1) as pioneered by Bielawski and coworkers, 10 should fulfill these requirements for a spacer.…”

Recent Developments in the Applications of Palladium Complexes Bearing N-Heterocyclic Carbene Ligands

“…Ever since, the coordination of these ligands has been extended to other metals such as rhodium, 105 iridium, 106 ruthenium, 107 iron 108 and nickel. 109 The first palladium complexes with linearly-opposed coordination were polymeric in nature.…”