Cyclic iron tetra N-heterocyclic carbenes: synthesis, properties, reactivity, and catalysis

Abstract

Cyclic iron tetracarbenes structurally resemble iron porphyrins, but the strong equatorial σ-donation results in a different electronic structure and reactivity.

Synthesis, characterization, and biomedical evaluation of ethylene-bridged tetra-NHC Pd(ii), Pt(ii) and Au(iii) complexes, with apoptosis-inducing properties in cisplatin-resistant neuroblastoma cells

“…Due to the absence of similar macrocyclic imidazolinium compounds, H 4 L5 is compared to a and H 4 L8 in the following. 3 Relative to a, all signals of H 4 L5 and H 4 L8 are upeld shied, indicating a higher electronic density due to the +I effect of the ethylene bridge leading to an increased shielding effect in the NMR. 10,26 The higher upeld shi of H 4 L5 compared to H 4 L8 can be explained by the electronic inducing effect of the saturated bond.…”

“…Changing one or more structural properties of a NHC ligand can lead to signicantly different reactivities and stabilities of the resulting complexes. 3 Oen several NHC units are combined in multidentate ligands, making use of the chelating effect, and a plethora of multidentate NHC metal complexes has been reported. 4,5 Our group has developed several bidentate and cyclic tetradentate NHC ligands.…”

“…in medicinal chemistry 6,7 and epoxidation catalysis. 3 While the bidentate ligands can form open-chain tetracarbene complexes, 8,9 the tetradentate ligands give cyclic tetracarbene compounds. Most commonly applied in our recent examinations is the calix [4]imidazolium ligand precursor (a, Fig.…”

“…10 Its iron complex (c) can be used as olen epoxidation catalyst achieving unprecedented activity. 3 Coinage metal tetracarbene complexes (and metal NHC complexes in general [11][12][13][14][15][16][17] ) have been investigated regarding their antiproliferative activity and selectivity against cancer cells (b, d-f, Fig. 1).…”

Tuning the polarity of charge carriers in N-heterocyclic carbene-based single-molecule junctions via atomic manipulation

“…30,31 NHCs are gaining increased research attention owing to their capability to form inert bonds with several metals. [32][33][34][35][36] Functionalized NHC complexes have applications in surface protection, catalysis, drug protection/delivery, phosphorescence, and electronics. [37][38][39][40][41][42] Furthermore, an NHCmodified Au surface can potentially be used in single-molecular devices because of its lowered work function.…”