Synthesis and Characterization of a Manganese(III) Complex with a Tetradentate N-Heterocyclic Carbene Ligand

Abstract

An imidazolium salt, containing two aryloxy groups, was prepared as a precursor for the tetradentate dicarbene ligand. The complexation with Mn(OAc) 2 gaVe an air-stable Mn(III) N-heterocyclic carbene complex in moderate yield. The crystal structure of the complex shows a distorted-squarepyramidal structure, in which two carbene carbon atoms and two aryloxy oxygen atoms of the tetradentate carbene ligand occupied the basal plane.

A Novel Carbene Ruthenium Complex as Reusable and Selective Two‐Electron Catalyst for Alkene Epoxidation

“…Olefin epoxidation is a key chemical transformation for the synthesis of highly functionalized organic species and the use of several transition metal complexes for this type of process has been well documented 12. Among these, the use of NHC as ligands for epoxidation catalysts has been investigated mainly with Mo species13 and also with a few examples of Mn14 or W13a complexes but, although Ru complexes are powerful catalysts broadly studied for epoxidation processes in homogeneous catalysis,15 a unique example of epoxidation mediated by a Ru‐NHC catalyst has been reported to date 11a…”

“…[9d-e,11] Olefin epoxidation is a key chemical transformation for the synthesis of highly functionalized organic species and the use of several transition metal complexes for this type of process has been well documented. [12] Among these, the use of NHC as ligands for epoxidation catalysts has been investigated mainly with Mo species [13] and also with a few examples of Mn [14] or W [13a] complexes but, although Ru complexes are powerful catalysts broadly studied for epoxidation processes in homogeneous catalysis, [15] a unique example of epoxidation mediated by a Ru-NHC catalyst has been reported to date.[11a]On the other hand, heterogenization and reuse of catalysts are fields of unquestionable importance especially towards their application in large-scale processes.[16] Room-temperature ionic liquids (RTIL) have been broadly studied as alternative solvent or co-solvent media in catalysis [17] given their ease of manipulation, high solubilization capacity and the possibility of easily tuning the RTILs properties by changing the cation, the anion or the attached substituents. Several oxidative catalytic processes have been tested…”

Theoretical Investigation of Promising Molecules for Obtaining Complexes with Planar Tetracoordinate Carbon

“…The distances of two Mn–C bonds in 5 are 2.037 and 1.920 Å, respectively, which are consistent with the Mn–C bond length (2.015 and 1.984 Å) in the Mn(III) complex with a tetradenate NHC ligand. 59…”

Manganese-N-heterocyclic carbene (NHC) complexes – An overview

“…Another similar manganese(III) complex was developed in the same year using a tetradentate NHC ligand (Fig. 19) [74]. The structure of the complex was determined to be square-pyramidal by means of single-crystal X-ray diffraction.…”