Reactions of [FeL2(CH3CN)2](PF6)2 (L = N-pyrimid-2-ylimidazol-ylidene) with N-, P-, O-, and S-donors and its catalytic activity

Abstract

Reactions of [FeL 2 (CH 3 CN) 2 ] 2+ (L = N-pyrimid-2-ylimidazolylidene) with various N-, P-, O-, and S-donors were investigated. By replacing the labile acetonitrile, various iron-NHC complexes containing additional N-, P-, O-, and S-ligands were prepared. All the iron-NHC complexes were fully characterized by NMR spectroscopy and X-ray crystallography. [30,31], the organometallic chemistry of iron-NHC complexes has not been well explored. We [32] recently reported that iron-NHC complexes can be prepared from iron powder with imidazolium salts or an Ag-NHC complex in air. Alternatively, iron-NHC complexes can be electrochemically prepared using an imidazolium salt as the supporting electrolyte [33]. These synthetic procedures allow for scaling the preparation of iron-NHC complexes, and thus offer more opportunity for careful investigation of the reactivity and application of iron-NHC complexes. In this paper, we report the reactions of [FeL 2 (CH 3 CN) 2 ] 2+ (L=N-pyrimid-2-ylimidazolylidene) with N-, P-, O-, and S-donors and the structural characterization of resulting iron(II)-NHC complexes.

Organometallic 3d transition metal NHC complexes in oxidation catalysis

“…Besides the formation of a μ 2 -oxo bridged Fe III -O-Fe III dimer, methylene bridge C-H oxidation is described. 100,101 For NHC supported iron catalysts, irreversible ligand protonation at the carbene C-donors with subsequent dissociation and/or oxidation of the ligand could be possible. 100 As mentioned before, degeneration over the Fe III -O-Fe III dimer can be excluded due to the regeneration with Lewis acids.…”

“…100,101 For NHC supported iron catalysts, irreversible ligand protonation at the carbene C-donors with subsequent dissociation and/or oxidation of the ligand could be possible. 100 As mentioned before, degeneration over the Fe III -O-Fe III dimer can be excluded due to the regeneration with Lewis acids. Methylene bridged oxidation can also be ruled out by ESI-MS analysis and comparative catalytic epoxidation experiments by employing an analogue of 11b with deuterated methylene bridges, where no distinct differences in performance are observed.…”

Chemistry of IronN-Heterocyclic Carbene Complexes: Syntheses, Structures, Reactivities, and Catalytic Applications

“…On the basis of 87a, a variety of complexes were synthesized with an overview provided in Scheme 19. 57 The reactivity study on 87a focused on displacement of the acetonitrile solvent molecules in 87a using bidentate ligand motifs, which resulted in preservation of the sawhorse-like structure in all cases. 88 was obtained in 48% yield by reaction of 87a with pyridine-2thiol and K 2 CO 3 , exhibiting the thiolate trans to an NHC.…”

Recent advances in iron-catalysed cross coupling reactions and their mechanistic underpinning

“…For example, Chen and coworkers were able to produce desired biaryl coupling products in moderate yields when catalysed by a dicationic iron(II) supported by a bidentate pyrimidine NHC ancillary ligand. 14 Another instance of N-heteroaromatic halide coupling was published by the Knochel group in which iron halide salts and careful solvent selection were enough to produce the desired product in excellent yields (Scheme 2). 15 They were able to enhance reaction performance by replacing the traditional Grignard reagent with a lithium-chloride adduct.…”