Synthesis and Catalytic Properties in Olefin Epoxidation of Octahedral Dichloridodioxidomolybdenum(VI) Complexes Bearing N,N‐Dialkylamide Ligands: Crystal Structure of [Mo₂O₄(μ₂‐O)Cl₂(dmf)₄]

Abstract

The catalytic performance of the complexes -diethylformamide (def) and N,N-diphenylformamide (dpf)] was examined in the epoxidation of cis-cyclooctene with tert-butyl hydroperoxide (tbhp) at 55°C and in the absence of a cosolvent. The complexes showed high turnover frequencies in the range of 561-577 mol mol Mo -1 h -1 , giving the epoxide as the only product in Ն98 % yield after 6 h. The reaction rates decreased significantly in consecutive runs carried out by recharging the reactors with olefin and oxidant. On the basis of the IR spectroscopic characterisation of the solids recovered at the end of the catalytic reactions, the decrease in activity is attributed to the formation of dioxido(µ-oxido)-

Use of MoO2Cl2(DMF)2 as a precursor for molybdate promoted hydrolysis of phosphoester bonds

“…The absence of strong bands in the region of 700-850 cm −1 seems to exclude the existence of μ 2 -bridging oxide groups (Mo-O-Mo). 34 Indeed, the pattern of bands for the Mo-O vibrations matches that typically exhibited by molybdenum trioxide hydrates of the type MoO 3 •nH 2 O (n = 0.5, 1.0), 35 or molybdenum oxide/organic composite materials containing inorganic chains built up from edge-shared distorted {MoO 6 } octahedra. 29,36 A band at 1663 cm −1 for 2 indicates the presence of the coordinated carbonyl group of dimethylformamide (free DMF presents a band at 1675 cm −1 ).…”

Hydrogen bond donor functionalized dioxido-molybdenum(VI) complexes as robust and highly efficient precatalysts for alkene epoxidation

“…Furthermore, the high activity in tert-butanol is especially surprising, as tert-butanol usually impedes epoxidation activity with many other published precatalysts. [18,28] In comparison with structurally related, previously reported μ-oxido bridged complexes (bearing hydrogen bond acceptor functionalities such as -OMe and -NMe2), [18] the high activity and functional group tolerance of the complexes herein clearly suggest a beneficial role of the additional hydrogen bond donors on the ligand amide functionalities, which seems to be able to stabilize the oxidant and/or substrate molecules in the second coordination sphere. Another benefit of the presented system might be the increased lability of the donor arm, allowing for the functionalities in epoxidation catalysis and therefore clearly warrant a further exploration and implementation in systems for efficient and "green" homogeneous epoxidation catalysis.…”

“…Epoxidations in isopropanol and tert-butanol show higher catalytic activity (75 and 89% conversion of S1, entry 5 and 6), despite the fact that tertbutanol is known to be an inhibitory by-product in epoxidations with TBHP as oxidant. [18,28] Mononuclear methoxido complexes 2, 4 and 6 have proven to be less active in epoxidation compared to their dinuclear congeners 1, 3, 5 and 7, suggesting that the dinuclear complexes are stable in isopropanol or tert-butanol and are not cleaved to the corresponding mononuclear alkoxido complexes (vide supra).…”

Heterogenization of a molybdenum Schiff base complex as a magnetic nanocatalyst: An eco-friendly, efficient, selective and recyclable nanocatalyst for the oxidation of alkenes

“…This observation indicates the involvement of the azomethine nitrogen in coordination with the molybdenum center [44]. The IR spectra of the Mo complex showed two characteristic strong bands in the regions 826 and 900 cm À1 , which could be assigned to the symmetric and asymmetric stretching vibrations of cis-dioxo (MoO 2 ), respectively [45][46][47][48].…”