Bis(N‐heterocyclic carbene) Dipalladium Complexes: Synthesis, Solid‐State Conformational Studies and Solution Behaviour

Abstract

New palladium(II) bis(N-heterocyclic carbene) (NHC) complexes have been prepared via metallomacrocyclic Ag I ligand transfer agents. Reaction of 1,4-bis(3-isopropylimidazolium)xylene (1a) hexafluorophosphate with Ag 2 O gives a Ag I macrocyclic NHC complex in which two silver ions are sandwiched between two dipodal ligands (2a). The NHC moieties adopt a cisoid conformation relative to one another. Upon transfer to palladium to give [{PdCl 2 (MeCN)} 2 (bis-NHC)] (3a) the NHC ligands in the complexes adopt a mixture of cisoid and transoid conformers in the solid state,

Enhanced cytotoxicity of silver complexes bearing bidentate N-heterocyclic carbene ligands

“…23,24 Reactions were generally performed in dichloromethane, with the bromide salts precipitating within 1 hour. Counterion exchange was performed using NH 4 BF 4 in methanol.…”

“…N-substituted imidazoles, imidazolium salts, and compound 5d were prepared according to literature procedure. 23,24,29 Manipulations were performed using (5a) 1a (522 mg, 1.24 mmol) was added to DCM (7 mL) giving a white suspension. To the suspension was added MeOH (1 mL) to give a clear solution to which was added Ag 2 O (432 mg, 1.86 mmol) and 3 Å molecular sieves.…”

Silver carbene complexes: An emerging class of anticancer agents

“…In adenocarcinomas MCF-7 (breast) and DLD1 (colon) cancer cell lines, these bidentate compounds are cytotoxic ( Figure 3). The synthesis of bis(imidazolium) hexafluorophosphate and tetrafluoroborate salts of silver using Ag 2 O is also reported (Lin & Vasam, 2007;Willans et al, 2009). These studies demonstrate that bidentate complexes are superior in MCF-7 than monodentate macrocyclic ligands due to their increased stability.…”

“…These studies demonstrate that bidentate complexes are superior in MCF‐7 than monodentate macrocyclic ligands due to their increased stability. Structure–activity relationship (SAR) of bidentate complexes 6 – 9 , concerning the position of NHC, demonstrate that the N‐substituent and counter ion had little influence on cytotoxicity in MCF‐7 (breast) cancer cell lines or their physical properties, such as solubility and diffusion parameters (Willans et al, ). Bidentate complexes 7a and 7c exhibited IC 50 values comparable with cisplatin in DLD1 (colon) whereas in MCF‐7 (breast) they are 4‐times more active.…”

Oxidative halogenation of dinuclear N-heterocyclic dicarbene gold(I) complexes

“…The gold(I) complexes 1 o and 1 m and the gold(III) complex 2 Br m were prepared according to literature procedures [5a,7,8a]. PhICl 2 and the imidazolium salt 1,1 0 -dimethyl-3,3 0 -(pxylylene)diimidazolium dibromide were prepared following the literature procedures [14,15]. NMR spectra were recorded on a Bruker Avance 300 MHz (300.1 MHz for 1 H and 75.5 for 13 C); chemical shifts (d) are reported in units of ppm relative to the residual solvent signals.…”