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Hydrogenation and hydrogenolysis of furfural and furfuryl alcohol catalyzed by ruthenium(II) bis(diimine) complexes
Author(s) -
Gowda Anitha S.,
Parkin Sean,
Ladipo Folami T.
Publication year - 2012
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.2819
Subject(s) - chemistry , ruthenium , hydrogenolysis , furfuryl alcohol , steric effects , diimine , catalysis , medicinal chemistry , furfural , alcohol , stereochemistry , organic chemistry
The catalytic activity of ruthenium(II) bis(diimine) complexes cis ‐[Ru(6,6′‐Cl 2 bpy) 2 (OH 2 ) 2 ](Z) 2 ( 1 , Z = CF 3 SO 3 ; 2 , Z = (3,5‐(CF 3 ) 2 C 6 H 3 ) 4 B, i.e. BArF) and cis ‐[Ru(4,4′‐Cl 2 bpy) 2 (OH 2 ) 2 ](Z) 2 ( 3 , Z = CF 3 SO 3 ; 4 , Z = BArF) for the hydrogenation and/or the hydrogenolysis of furfural (FFR) and furfuryl alcohol (FFA) was investigated. The molecular structures of cis ‐[Ru(4,4′‐Cl 2 bpy) 2 (CH 3 CN) 2 ](CF 3 SO 3 ) 2 ( 3 ′) and dimeric cis ‐[(Ru(4,4′‐Cl 2 bpy) 2 Cl) 2 ](BArF) 2 ( 5 ) were characterized by X‐ray crystallography. The structures are consistent with the anticipated reduction in steric hindrance about the ruthenium centers in comparison with corresponding complexes containing 6,6′‐Cl 2 bpy ligands. While compounds 1 , 2 , 3 , 4 are all active and highly selective catalysts for the hydrogenation of FFR to FFA under modest reaction conditions, 3 and 4 showed decreased activity. This is best explained in terms of reduced Lewis acidity of the Ru 2+ centers and reduced steric hindrance about the metal centers of catalysts 3 and 4 . cis ‐[Ru(6,6′‐Cl 2 bpy) 2 (OH 2 ) 2 ](BArF) 2 ( 2 ) also displayed high catalytic efficiency for the hydrogenation of FFA to tetrahydrofurfuryl alcohol. Presumably, this is because coordination of C═C bonds of FFA to the ruthenium center is poorly inhibited by non‐coordinating BArF counterions. Interestingly, cis ‐[Ru(6,6′‐Cl 2 bpy) 2 (OH 2 ) 2 ](CF 3 SO 3 ) 2 ( 1 ) showed some catalytic activity in ethanol for the hydrogenolysis of FFA to 2‐methylfuran, albeit with fairly modest selectivity. Nonetheless, these results indicate that ruthenium(II) bis(diimine) complexes need to be further explored as catalysts for the hydrogenolysis of C―O bonds of FFR, FFA, and related compounds. Copyright © 2012 John Wiley & Sons, Ltd.