Anellated N‐Heterocyclic Carbenes: 1,3‐Dineopentylnaphtho[2,3‐d]imidazol‐2‐ylidene: Synthesis, KOH Addition Product, Transition‐Metal Complexes, and Anellation Effects

Abstract

Two novel anellated N-heterocyclic carbenes (NHC), 1,3-dineopentylnaphtho[2,3-d]imidazol-2-ylidene, and 1,3-dineopentyl-2-ylido-imidazolo[4,5-b]pyridine were obtained by reduction of the respective thiones with potassium, the former also by deprotonation of the corresponding naphthimidazolium hexafluorophosphate by using excess KH in THF. The use of equimolar amounts of KH provided an unexpected formal addition product of this NHC with KOH. X-ray crystal structure analysis of the adduct provided evidence for a distorted tetrameric N-heterocyclic alkoxide, stabilized by two THF molecules. In C(6)D(6) the compound undergoes disproportionation. Transition-metal complexes [(NHC)AgCl], [(NHC)Rh(cod)Cl], and (E)-[(NHC)(2)PdCl(2)] of the novel naphthimidazol-2-ylidene were synthesized. X-ray crystal structures and (1)H and (13)C NMR spectroscopic data provided detailed structural information. Comparing characteristic data with those of nonanellated and differently anellated NHCs or their complexes provides information on the influence of the extended anellation.

Synthesis and Crystal Structures of New 1,3-Disubstituted Imidazoline-2-thiones

“…Typical reactions of these imidazoline-2-thiones include S-alkylation [34 -36], addition of halogen [37,38], oxidative desulfurization [4,10,39,40], reduction to the carbene [41,42], and formation of metal complexes [43 -45]. Numerous crystal structures of 1,3-disubstituted imidazoline-2-thione complexes with Al, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Ru, Rh, Ag, Cd, In, Sb, Te, W, Re, Ir, Au, Hg, Pb, and Bi were found in the Cambridge Structural Database (version 5.33, August 2012).…”

Sterically induced differences in N-heterocyclic carbene transition metal complexes

“…The ligand, N,N -bis-neopentylbenzimidazolin-2-ylidene, is reported to have its carbene carbon atom dislodged from the plane of the imidazole ring by 20.7(11) and 19.0(11) pm (two crystallographically different molecules in the asymmetric unit), respectively. A recent search of the CCSD reveals that such a dislocation is very rare for coordinated carbene ligands and if it occurs is limited to a few pm [9,[79][80][81][82][83]. However, for the higher homologues, N-heterocyclic silylenes NHSi [84][85][86][87][88][89] and germylenes NHGe [26,90,91] the occurrence is far more frequent and appears to be the rule for annelated NHSi and NHGe.…”

N -Heterocyclic Carbene Metal Complexes as Bio-Organometallic Antimicrobial and Anticancer Drugs

“…Until now there is a large number of NHC frameworks known in the literature, ranging from five-membered to seven-membered rings including, imidazolium (1), imidazolinium (2, 8) [40,41], triazolium (3) [42], oxazolium (4) [43,44], thiazolium (5) [45,46], pyrrolidium (6) [47][48][49][50], benzimidazolium (7) [51,52], bisoxazoline (9) [53], quinoxaline (10a) [54], naphtha annulated imidazolium (10b) [55], diazaphosphetidin amine (11) [56], pyrimidine (12) [57,58], perimidine (13) [59], dibenzo(1,3)diazepine (14) [60], imidazopyridine (15,16) [61], 2,2′-bipyridine derived imidazolium (17) [62], bis-imidazolium with arene backbone (18) [63], etc. as shown in www.future-science.com 1307 future science group N-heterocyclic carbene metal complexes as bio-organometallic antimicrobial & anticancer drugs Review coordination properties.…”