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Single‐Pot Ethane Carboxylation Catalyzed by New Oxorhenium(V) Complexes with N,O Ligands
Author(s) -
Kirillov Alexander M.,
Haukka Matti,
Kirillova Marina V.,
Pombeiro Armando J. L.
Publication year - 2005
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200505092
Subject(s) - chemistry , catalysis , carboxylation , acetic acid , medicinal chemistry , yield (engineering) , trifluoroacetic acid , selectivity , solvent , ligand (biochemistry) , methanol , iminodiacetic acid , chelation , organic chemistry , biochemistry , materials science , receptor , metallurgy
The oxorhenium(V) chelates [ReOCl(N,O‐L)(PPh 3 )] [N,O‐L=( O CH 2 CH 2 ) N (CH 2 CH 2 OH)(CH 2 CO O ) ( 2 ), ( O CH 2 CH 2 ) N (CH 2 CO O )(CH 2 COOCH 3 ) ( 3 )] and [ReOCl 2 (N,O‐L)(PPh 3 )] [N,O‐L=C 5 H 4 N (CO O ‐2) ( 4 ) C 5 H 3 N (COOCH 3 ‐2)(CO O ‐6) ( 5 )] have been prepared by reaction of [ReOCl 3 (PPh 3 ) 2 ] ( 1 ), in refluxing methanol, with N,N ‐bis(2‐hydroxyethyl)glycine [bicine; N(CH 2 CH 2 OH) 2 (CH 2 COOH)], N ‐(2‐hydroxyethyl)iminodiacetic acid [N(CH 2 CH 2 OH)(CH 2 COOH) 2 ], picolinic acid [NC 5 H 4 (COOH‐2)] or 2,6‐pyridinedicarboxylic acid [NC 5 H 3 (COOH‐2,6) 2 ], respectively, with ligand esterification in the cases of 3 and 5 . All these complexes have been characterized by IR and multinuclear NMR spectroscopy, FAB + ‐MS, elemental and X‐ray diffraction structural analyses. They act as catalysts, in a single‐pot process, for the carboxylation of ethane by CO, in the presence of potassium peroxodisulfate K 2 S 2 O 8 , in trifluoroacetic acid (TFA), to give propionic and acetic acids, in a remarkable yield (up to ca. 30%) and under relatively mild conditions, with some advantages over the industrial processes. The picolinate complex 4 provides the most active catalyst and the carboxylation also occurs, although much less efficiently, by the TFA solvent in the absence of CO. The selectivity can be controlled by the ethane and CO pressures, propionic acid being the dominant product for pressures about ca. 7 and 4 atm, respectively (catalyst 4 ), whereas lower pressures lead mainly to acetic acid in lower yields. These reactions constitute an unprecedented use of Re complexes as catalysts in alkane functionalization.