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Dioxidomolybdenum(VI) Complexes Containing Ligands with the Bipyrrolidine Backbone as Efficient Catalysts for Olefin Epoxidation
Author(s) -
Mayilmurugan Ramasamy,
Traar Pedro,
Schachner Jörg A.,
Volpe Manuel,
MöschZanetti Nadia C.
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201300258
Subject(s) - chemistry , catalysis , olefin fiber , molybdenum , medicinal chemistry , octahedron , phenol , mass spectrometry , crystal structure , crystallography , stereochemistry , organic chemistry , chromatography
Air‐stable chiral dioxidomolybdenum(VI) complexes of the type [MoO 2 (L)] (L = L1 2– ; 1 , L = L2 2– , 2 ) were prepared by the reaction of [MoO 2 Cl 2 ] with the bis(phenol) ligands 1,4‐bis(2‐hydroxy‐benzyl)‐( S , S )‐2,2′‐bipyrrolidine [( S , S )‐H 2 L1 ] and 1,4‐bis(2‐hydroxy‐3,5‐di‐ tert ‐butylbenzyl)‐( S , S )‐2,2′‐bipyrrolidine [( S , S )‐H 2 L2 ). They were characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single‐crystal X‐ray diffraction analysis, which revealed a distorted octahedral coordination geometry around the molybdenum(VI) center with a cis ‐α configuration. The Mo–O oxo bond lengths are almost equal and vary only between 1.701 and 1.7091 Å. Complexes 1 and 2 were found to be efficient and selective catalysts for various olefin epoxidation reactions. Catalyst loadings of 0.5 mol‐%, the use of 2 equiv. of oxidant ( tert ‐butyl hydroperoxide), as well as unchanged catalyst performance over three consecutive catalytic runs demonstrate the excellent stability of the catalysts. Various challenging substrates including 1‐octene or limonene were converted selectively to their corresponding epoxides. However, no asymmetric induction was observed.