Recent Progress in the Heterogenization of Complexes for Single‐Site Epoxidation Catalysis

Abstract

Epoxides are of central importance in organic synthesis since they provide access to a series of different 1,2‐difunctionalized intermediates starting from cheap olefins. Olefin epoxidation is catalyzed by a whole bunch of transition metal elements in high oxidation states, the most important are molybdenum, tungsten, rhenium and manganese. Organic peroxides, hydrogen peroxide bleach and even dioxygen have been used as the source of the oxygen atom that is transferred to the olefin. The present microreview summarizes the recent developments in terms of catalyst heterogenization for olefin epoxidation. Such strategies are requested for green synthesis protocols and are of special interest for expensive catalysts derived, e. g. from rhenium or complex chiral ligands.

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

“…Direct propene epoxidation over the Zr_NCCN, Zr_NCCNO, and Zr_ONCCNO catalysts was described in our earlier report. 16 Similar techniques could potentially be used to tether our organometallic complexes to a support, thereby providing heterogenized forms. b These results correct an error appearing in ref.…”

“…[11][12][13][14][15][16][17][18] Particles of different metals as well as their binary combinations were deposited on various matrices and tested for direct propene epoxidation. [11][12][13][14][15][16][17][18] Particles of different metals as well as their binary combinations were deposited on various matrices and tested for direct propene epoxidation.…”

Metal oxide-triazole hybrids as heterogeneous or reaction-induced self-separating catalysts

“…The principal approach to solving this problem has been the immobilization of molecular catalysts onto organic, inorganic or hybrid organic-inorganic supports [3][4][5][6]. However, the resultant materials suffer from a number of drawbacks, which include catalyst ''leaching", leading to deactivation, and poor accessibility of the active sites for the substrate.…”

Dioxomolybdenum(VI) and -Tungsten(VI) Amino Bisphenolates as Epoxidation Catalysts

“…Considering these important biological functions, many examples of molybdenum-and tungsten-containing model compounds for OAT have been studied [6][7][8][9][10]. Similarly, a number of artificial dioxomolybdenum(VI) and -tungsten(VI) complexes have been prepared for catalytic applications in important industrial processes, for example olefin epoxidation [11][12][13]. Such complexes can be also considered as soluble molecular models for metal oxide catalysts [14].…”