Discrete mononuclear and dinuclear compounds containing a MoO₂²⁺core and 4-aminobenzhydrazone ligands: synthesis, structure and organic-solvent-free epoxidation activity

Abstract

New aroylhydrazone molybdenum(vi) complexes have been synthesized, characterized and used as (pre)catalysts for epoxidation of cyclooctene using aqueous TBHP as the oxidant.

Implication of oxidant activation on olefin epoxidation catalysed by Molybdenum catalysts with aroylhydrazonato ligands: Experimental and theoretical studies

“…For dinuclear structures absorption bands in the range of 870 -900 cm -1 confirm that the coordination sphere of molybdenum is completed by the nitrogen atom from the neighbouring complex molecule, as already noticed for similar compounds. [8,9] For the complex 2•MeCN, absorption maximum characteristic for MeCN was not noticed in the IR spectrum, while the band at 2340 cm -1 was present in the spectrum of 3•MeCN. The presence of the MeCN in 2•MeCN was later confirmed by TG analysis.…”

“…This behaviour is well established in previous works. [8,9,22] Regarding the geometry of the ligand and the coordination sites, all analysed complexes ultimately possess the same tautomeric form and overall shape. Bond lengths (Table S3) suggest enol-imino form in the hydrazide functional group, as well as enolate form of chelating hydroxyaryl unit.…”

“…[4,5] Furthermore, mono-, di-or poly-nuclear Mo complexes with pyridoxal-or salicylaldehyde-based ligands, as ONS or ONO coordinating ligands, justified excellent catalytic performance following green experimental policies. [6][7][8][9] Recently, dinuclear aminobenzhydrazonato Mo(VI) complexes were proved to be very efficient epoxidation catalysts. [8] Consequently, we have continued further investigation in the quest for a more active catalyst towards understanding the possible epoxidation mechanism.…”

Efficient Molybdenum Hydrazonato Epoxidation Catalysts Operating under Green Chemistry Conditions: Water vs. Decane Competition

“…In the proposed quest, our research follow-up was to obtain efficient molybdenum epoxidation catalysts containing benzaldehyde-based hydrazones (Scheme 1). The choice of ligands lies in the fact that the similar molybdenum complexes showed good activity and were classified as efficient catalytic systems [11][12][13]. In the presented research, the stress was on the use of 2-hydroxy-benzhydrazide derivatives, that could provide catalytically active molybdenum complexes.…”

Replacement of Volatile Acetic Acid by Solid SiO2@COOH Silica (Nano)Beads for (Ep)Oxidation Using Mn and Fe Complexes Containing BPMEN Ligand

“…The use of chlorinated solvents such as dichloroethane (DCE), a highly toxic solvent, has to be avoided [ 15 ]. In the research group, the processes have been found to be active without organic solvent using complexes with tridentate ligands [ 16 , 17 , 18 , 19 , 20 ] or polyoxometalates (POMs) [ 21 , 22 , 23 ], giving a first step towards a cleaner process. The oxidant used in this case is tert -butyl hydroperoxide (TBHP) in aqueous solution.…”