1,1′-(Pyridine-2,6-diyl)bis(3-benzyl-2,3-dihydro-1H-imidazol-2-ylidene), a new multidentate N-heterocyclic biscarbene and its silver(I) complex derivative

Synthetic and Structural Studies of Silver(I)‐ and Gold(I)‐ContainingN‐Heterocyclic Carbene Metallacrown Ethers

“…[15] However, a more convenient procedure to synthesize a variably bridging bis(imidazolium) salt for the prepara- tion of NHC-metal complexes has been developed in which a dihalide and two molecules of N-substituted imidazole are used. The bridging spacer linking the two imidazolium units includes methylene, ethylene, [16,17] o,p-phenylenebis-(methylene), [18] pyridinediyl, [19,20] an optically active 1,2-cyclohexyldiamine-derived linker, [21] and a pyridine-2,6-diylbis(methylene) linker (Scheme 1). [22][23][24][25][26] However, bis(imidazolium) salts with a flexible bridge have seldom been investigated.…”

Synthesis of heteroaromatic 3,3′-bridged biscarbenes of the 1,2,4-triazole series and their properties

“…The syntheses of biscarbenes of the 1,2,4-triazole series were carried out in three steps: (1) the bis-1,2,4-triazoles 2а-с were obtained by ring transformations of the bis-1,3,4-oxadiazoles 1а-с with anilines; (2) subsequent quaternization of the 1,2,4-triazoles 2а-с with 1-bromoadamantane or tert-butyl iodide afforded the bis-1,2,4-triazolium salts 3а-d; (3) finally, the bis-1,2,4-triazol-5-ylidenes 5а-d were prepared by deprotonation of salts 3а-d by treatment with bases. The first stage of the process has already been described 7 and involves the ring transformation of arylenbis-1,3,4-oxadiazoles 1а,b and butylen-bis-1,3,4-oxadiazole 1с with aniline trifluoroacetate in о-dichlorobenzene at 200 ºС thus affording bistriazoles 2a-с.…”

“…Bisimidazol-2-ylidenes which are linked via nitrogen atoms and an aliphatic bridge have been used for the in situ chelation of metal cations. Bisimidazol-2-ylidenes featuring a pyridine ring have also been described 3,4 and used for the preparation of carbene chelated complexes. However, stable carbenes of the 1,2,4-triazole series with conjugated bonds between the carbene moieties were unknown until recently.…”

Stable heteroaromatic carbenes of the benzimidazole and 1,2,4-triazole series

“…Caballero et al 17 reported a silver complex of bisimidazol-2-ylidene with a pyridine bridge; however, this complex is not polymeric. While the silver complexes described by Chen et al 44 and Melaiye et al 45 are oligomeric clusters, these complexes do not involve conjugation.…”

“…This method has proved successful for the synthesis of a variety of imidazol-2-ylidenes and biscarbenes 14,15 . Subsequently, other new types of stable carbenes and biscarbenes have been synthesized (for example pyridine-containing carbenes 16 , biscarbenes 17,18 , and carbenes of the pyrimidine 12 and perimidine 19 series). The recent synthesis by Hahn et al 20 of stable, non-aromatic imidazolin-2-ylidenes, which are sterically protected on one side, and the modification of the carbene structure by the nucleophilic substitution of a phosphonio group in a phosphonioarylcarbene 21 are especially interesting.…”