Synthesis and catalytic epoxidation potential of oxodiperoxo molybdenum(VI) complexes with 2-hydroxybenzohydroxamate and 2-hydroxybenzoate: the crystal structure of PPh4[MoO(O2)2(HBA)]

Abstract

PPh 4 ) 2 [MoO(O 2 ) 2 (SHAH)]ÁH 2 O and PPh 4 [MoO-(O 2 ) 2 (HBA)] (SHAH 3 = 2-hydroxybenzohydroxamic acid and HBAH = 2-hydroxybenzoic acid) have been synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the second complex has been structurally characterized by single-crystal X-ray diffraction analysis. We have compared the catalytic activities of these two new complexes, together with the previously reported PPh 4 [MoO(O 2 ) 2 (BZ)] (BZH = benzoic acid), with respect to the epoxidation of alkenes. The hydroxamate complex is the most efficient catalyst among the three complexes, showing excellent catalytic activity for the substrates cyclohexene, cyclooctene, cinnamyl alcohol, pent-4-en-1-ol and hex-1-ene.

Ionic Liquids Based on Oxidoperoxido-Molybdenum(VI) Complexes with a Chelating Picolinate Ligand for Catalytic Epoxidation

“…The CV and DPV analysis indicated that variation of the cation structure does not significantly affect the electrochemical properties of the complex anion. This is the only catalytic study which follows the studies by Garah et al [31,32,34,60] for [Cat] m [MoO(O 2 ) 2 (L) n ] type complexes as epoxidation catalysts using TBHP as oxidant. The type of cation may influence the catalytic performance.…”

“…Later, in 2005, Maiti et al [13] reported the anionic complex [PPh 4 ][MoO(O 2 ) 2 (QO)], with QOH = 8-quinolinol, as an active catalyst for the oxidation of alcohols, sulphides and amines using H 2 O 2 as oxidant. However, in the same decade, Garah et al [31,32,34,60] found that several monoanionic complexes of the type [Cat][MoO(O 2 ) 2 (L) n ] ([Cat] + = tetraorganophosphonium type cation, and L = conjugated base of 2-hydroxybenzoic acid, benzoic acid [31], pyridine-2-carboxylic acid [32], or an oxime such as (hydroxyphenyl)ethenone [60], salicylaldoxime [34] and pyridine-2-carboxaldoxime [32]) were inactive as catalysts for olefin epoxidation using H 2 O 2 as oxidant (co-additives were required for olefin epoxidation to occur).…”

“…Neutral Mimoun type mononuclear complexes are well established catalysts for olefin epoxidation, as highlighted in several reviews [6,7,[26][27][28][29]. These catalytic systems may use eco-friendly oxidants such as hydrogen peroxide [3,4,[30][31][32][33][34][35][36][37][38] and tert-butyl hydroperoxide (TBHP) [8,30,35,[39][40][41][42][43][44][45], and different types of solvents: catalyst/H 2 O 2 systems with organic solvents [3,4,[30][31][32][33][34], water [35], ionic liquids [36,37,46] or without solvent [38]; and catalyst/TBHP systems with an organic solvent [8,30,[39][40][41][47][48][49][50]…”