Molybdenum (VI) Complexes Containing Pyridylimine Ligands: Effect of the Imine Nitrogen Substituent in the Epoxidation Reaction

Abstract

A series of pyridylimine ligands with variations of the substituent at the imine nitrogen were synthesized and coordinated to the [MoCl 2 O 2 ] core. The novel molecular structures of the complexes were fully characterized by 1 H and 13 C NMR, FT-IR, ESI, EA, and X-ray crystallography, and their catalytic activity was studied for the epoxidation of alkenes using tert-butyl hydroperoxide (TBHP) as the oxidant. The new complexes showed excellent catalytic activity and fine selectiv-ity in the epoxidation reaction compared with similar homogeneous molybdenum complexes. The results demonstrated that there is a significant change in the catalytic performance, depending on the alkyl arm on the structure of the pyridilimine ligand. The catalytic results indicated that complex [MoCl 2 O 2 (L)] (L: N-(2-Pyridinylmethylene)-1-tert-butylimine) C 5 is the best catalytic precursor in the epoxidation of cyclohexene (TON: 92920 and TOF: 30974 h À 1).

Diastereomeric Separation of Chiral fac-Tricarbonyl(iminopyridine) Rhenium(I) Complexes and Their Cytotoxicity Studies: Approach toward an Action Mechanism against Glioblastoma

“…The diimine ligands ( 1–4a ( R ) / 1–4b ( S ) ) were all synthesized according to a similar procedure. , The complexes were prepared by the reaction of equimolar amounts of the chiral ( R / S )-diimine ligand and Re­(CO) 5 Br in boiling acetonitrile under a nitrogen atmosphere for 24 h, affording orange solids (Scheme ). The crude product was recollected by filtration and purified by several washes with pentane to provide the rhenium complexes in excellent yields (80–90%).…”

“…Synthesis of the chiral iminopyridine ligands was carried out according to the literature method. 38 A stoichiometric amount of the corresponding chiral amines was added to a stirred solution of 2-pyridinecarboxaldehyde (250 μL, 2.65 mmol) in acetonitrile (20 mL) with molecular sieves (4 Å). After stirring overnight at room temperature, the reaction was filtered off, washed with CH 2 Cl 2 (3 × 15 mL), and dried in vacuum.…”

C2 and C1‐Symmetric Camphopyrazole Dioxomolybdenum(VI) Complexes catalyze the Epoxidation of Cyclic Olefins

“…Their performance strongly depends on their solubility and the steric and electronic factors exerted by the ligands. Complexes with N−N bidentate ligands, such as substituted pyridines, [13,14,15,16] Schiff bases, [17,18,19,20] have traditionally proven to be highly active and selective in such processes. More recently, complexes with pyrazole‐based ligands have come up in this area [21,22,23,24,25,26,27] .…”