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Iron( II ) Complexes with Bio‐Inspired N,N,O Ligands as Oxidation Catalysts: Olefin Epoxidation and cis ‐Dihydroxylation
Author(s) -
Bruijnincx Pieter C. A.,
Buurmans Inge L. C.,
Gosiewska Silvia,
Moelands Marcel A. H.,
Lutz Martin,
Spek Anthony L.,
van Koten Gerard,
Klein Gebbink Robertus J. M.
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200700573
Subject(s) - chemistry , dihydroxylation , ligand (biochemistry) , catalysis , hydroxylation , heme , dioxygenase , stereochemistry , propionate , olefin fiber , combinatorial chemistry , enzyme , organic chemistry , biochemistry , enantioselective synthesis , receptor
Abstract The Rieske dioxygenases are a group of non‐heme iron enzymes, which catalyze the stereospecific cis ‐dihydroxylation of its substrates. Herein, we report the iron(II) coordination chemistry of the ligands 3,3‐bis(1‐methylimidazol‐2‐yl)propionate ( L1 ) and its neutral propyl ester analogue propyl 3,3‐bis(1‐methylimidazol‐2‐yl)propionate ( PrL1 ). The molecular structures of two iron(II) complexes with PrL1 were determined and two different coordination modes of the ligand were observed. In [Fe II ( PrL1 ) 2 ](BPh 4 ) 2 ( 3 ) the ligand is facially coordinated to the metal with an N,N,O donor set, whereas in [Fe II ( PrL1 ) 2 (MeOH) 2 ](OTf) 2 ( 4 ) a bidentate N,N binding mode is found. In 4 , the solvent molecules are in a cis arrangement with respect to each other. Complex 4 is a close structural mimic of the crystallographically characterized non‐heme iron( II ) enzyme apocarotenoid‐15–15′‐oxygenase (APO). The mechanistic features of APO are thought to be similar to those of the Rieske oxygenases, the original inspiration for this work. The non‐heme iron complexes [Fe II ( PrL1 ) 2 ](OTf) 2 ( 2 ) and [Fe II ( PrL1 ) 2 ](BPh 4 ) 2 ( 3 ) were tested in olefin oxidation reactions with H 2 O 2 as the terminal oxidant. Whereas 2 was an active catalyst and both epoxide and cis ‐dihydroxylation products were observed, 3 showed negligible activity under the same conditions, illustrating the importance of the anion in the reaction.