Synthesis and Structure of Homoleptic Iron Complex Bearing Pincer-Type 1,2,3-Triazol-5-ylidene

Abstract

structure of pyridine-bridged 1,2,3-triazol-5-ylidene (3a, 3b), which are prepared from the corresponding bis(1,2,3-triazole) (1a, 1b) as the starting material, via the methylated bis(1,2,3-triazolium) salts (2a, 2b). The compounds 2a and 2b are easily reduced to form 3a and 3b, respectively, in good yields (Scheme 2) [23]. They are rare examples of the isolated MIC. The X-ray crystallography and DFT calculations of 3a indicated its characteristic amphiphilic nature; because it has an expanded π-conjugated plane including one pyridine and two carbene rings, the stabilized π*-orbital easily accept a single unpaired electron to form anionic radical species in part, despite the fact that carbene carbons are strong σ-donor [24]. Here, we successfully synthesized and determined the tridentate MIC complex of iron. Unexpectedly, even if stoichiometric amount of the carbene ligand was added to iron halides, two molecules of the carbene coordinated to form dicationic homoleptic iron complex 4 with stepwise liberation of two halide anions from iron halides. Materials and Methods All experiments were carried out under an inert gas atmosphere using standard Schlenk techniques and a glove box (MBraun UniLab) unless otherwise noted. THF, toluene, hexane, and benzene-d 6 were distilled from benzophenone ketyl and stored under a nitrogen atmosphere. Organic reagents used for coupling reactions were distilled just before use. The starting materials, 2,6-bisacetylpyridine [25] and 2-azido-2,6-diisopropylbenzene [26] were prepared according to the literature. 1 H NMR (400 MHz) and 13 C NMR (100 MHz) spectra were recorded on a Bruker AVANCE III HD 400 MHz spectrometer at room temperature in CDCl 3 or acetonitrile-d 3. Chemical shifts (δ) were recorded in ppm from the internal standard. IR spectra were recorded in cm-1 on a PERKIN ELMER Spectrum Two spectrometer equipped with a universal diamond ATR.

Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(ii) complexes

“…This interpretation is confirmed by the shortening of the Fe-C carbene bond length from 1.9665(3) Å in [Fe(bim) 2 ] 2+ to 1.9403(4) Å in Fe2. 8 The structural parameters, which are in line with those of [Fe(btp) 2 ] 2+ reported by Iwasaki et al 18 (btp = 2,6-bis(1-mesityl-2,3-triazol-5-ylidene)pyridine), therefore support the stronger s-donating character of MICs in comparison to classical NHCs. Bidentate ligands are advantageous to achieve a high octahedral symmetry.…”