The first macrocyclic abnormally coordinating tetra-1,2,3-triazole-5-ylidene iron complex: a promising candidate for olefin epoxidation

Abstract

The first macrocyclic and abnormally coordinating, mesoionic N-heterocyclic carbene iron complex has been synthesised and characterised via ESI-MS, EA, SC-XRD, CV, NMR and UV/Vis spectroscopy. 13C-NMR spectroscopy and CV measurements...

Using PMHS for Catalytic Hydrosilylation with Dimeric Iron Complexes Featuring Mesoionic Carbene Ligands

“…The complex features two tetrahedral iron centers, each coordinated with chelating L1 and one N­(SiMe 3 ) 2 ligand. The Fe–C trz bond lengths are 2.083(4) and 2.129(4) Å and thus longer than any of the previously measured Fe II –C trz bonds, which typically range between 1.92 and 2.04 Å. ,,,− …”

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

“…1), possessing an even more electron-rich iron center in this series, has been preliminarily investigated as pre-catalyst in epoxidation catalysis. 53 However, the first results indicate that 70 lags behind its model, complex 1, in terms of activity, as 70 reaches a TOF of 41 000 h À1 with Sc(OTf) 3 , whereas 1 exhibits a higher TOF (50 000 h À1 ) in the absence of any additive (Table 6). The highest conversion of 89% without additive is reached at À10 1C after 10 min, revealing a reduced stability at higher temperatures, like 1 and 2.…”

“…[47][48][49][50][51][52] The calix [4]1,2,3-triazole is subsequently methylated using MeOTf. 53 The imidazolium salts can be purified by anion exchange with the weakly coordinating anion hexafluorophosphate. This does not only increase the solubility of the macrocycle towards organic solvents, but also is an effective way to remove larger rings as side-products.…”

“…Selected catalytic performance of 1, 2 and 44 in the epoxidation of cis-cyclooctene53,73,75 All conversions and selectivities were determined by GC-FID after a reaction time of 5 min. b TOFs were determined after 10 s. c Catalyst concentration: 0.1 mol%, conversion was determined after 10 s. d Catalyst concentration: 0.5 mol%.…”

Application of first-row transition metal complexes bearing 1,2,3-triazolylidene ligands in catalysis and beyond

“…Kühn and coworkers have synthesized an iron complex with a trz-based macrocyclic ligand. 92 Treatment of ligand precursor L14 with two equivalents [Fe(HMDS) 2 (THF)] in MeCN at −40 °C, in which the HMDS ligands act as internal bases, yields complex Fe7 ( Scheme 20 ) together with [Fe(MeCN) 6 ](PF 6 ) 2 , as the iron salt is used in excess. The iron center in this complex is distorted octahedral with an equatorial tetradentate macrocyclic ligand and two axially coordinating MeCN ligands.…”