Synthesis of New Dipyrido-Annulated N-Heterocyclic Carbenes with Ortho Substituents

Abstract

A method for the introduction of various substituents at the 4 and 8 positions of 2,10-di-tert-butyldipyrido[1,2-c;2',1'-e]imidazolium salts, is described. The new imidazolium salts bearing substituents (R' = Cl, SPh) at the 4 and 8 positions are synthesized in three-step procedures, and carbenes generated from the imidazolium salts can be used to give the corresponding rhodium complexes. The role of the 4,8-substituents can be either bystanders or coordinating ligands according to the nature of the metal moiety.

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

“…and Kunz et al − Both theoretical and experimental studies have shown that its aromatic dipyrido moieties contribute to empty p orbitals of the carbene carbon, resulting in a higher π-donating ability in comparison to Arduengo-type NHCs . Previously, we have successfully introduced thio, phosphinyl, − and aryl substituents to the dpa NHC backbone. The aryl-substituted dpa Ar2 NHCs were in situ generated by deprotonation of the respective imidazolium salt and characterized by complexation to a gold­(I) center (Scheme ).…”

Synthesis of New Dipyrido‐Annulated N‐Heterocyclic Carbenes with Aryl Substituents

“…The targeted salts shown in Scheme were synthesized from the thiourea 2 (Scheme ) 5b,5c. Via dilithiation by t BuLi, electrophilic addition of (BrCl 2 C) 2 followed by methylation using MeI, 2 was converted into the dibromo‐substituted species 8 in 85 % yield, which was sufficiently pure to be used without further purification.…”

Luminescent Di- and Tetranuclear Gold Complexes of Bis(diphenylphosphinyl)-Functionalized Dipyrido-Annulated N-Heterocyclic Carbene

“…Among these, the ortho-diphosphinylsubstituted derivative (dpa P2 -NHC, Chart 1C) has only been characterized by coordination to a rhodium center previously. 34 This work reports the isolation and characterization of the dpa P2 -NHC for the first time. Its coordination chemistry to gold(I) complexes and the photoluminescent properties of the resulting multinuclear complexes are investigated.…”

“…Our group has successfully introduced thio, phosphinyl, and aryl groups into Weiss and Kunz’s − dipyrido-annulated N-heterocyclic carbene (dpa-NHC) to form pincer ligands. The steric rigidity , and unusual weak σ-donating, π-rich, and overall strong donating nature of the backbone as carbene are of special interest to us. Among these, the ortho -diphosphinyl-substituted derivative (dpa P2 -NHC, Chart C) has only been characterized by coordination to a rhodium center previously …”

“…The steric rigidity , and unusual weak σ-donating, π-rich, and overall strong donating nature of the backbone as carbene are of special interest to us. Among these, the ortho -diphosphinyl-substituted derivative (dpa P2 -NHC, Chart C) has only been characterized by coordination to a rhodium center previously …”