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Synthesis, Structures, and Transfer Hydrogenation Catalysis of Bifunctional Iridium Complexes Bearing a C–N Chelate Oxime Ligand
Author(s) -
Watanabe Megumi,
Kashiwame Yohei,
Kuwata Shigeki,
Ikariya Takao
Publication year - 2012
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.201100800
Subject(s) - chemistry , oxime , bifunctional , ligand (biochemistry) , transfer hydrogenation , acetophenone , medicinal chemistry , trifluoromethanesulfonate , iridium , catalysis , nitrile , polymer chemistry , organic chemistry , ruthenium , biochemistry , receptor
We have synthesized a series of organometallic oxime complexes as novel metal–ligand cooperating bifunctional catalysts. The reaction of [{Cp*IrCl(μ 2 ‐Cl)} 2 ] with ketoximes in the presence of sodium acetate afforded the half‐sandwich chlorido iridium complexes 6 bearing a C–N chelate oxime ligand with a protic OH group in the β‐position to the metal. Complex 6a , derived from acetophenone oxime, reacted with silver triflate to give the triflate complex 7 and cationic nitrile complex 8 depending upon the reaction solvent. Complexes 6 also reacted with a base in dichloromethane to afford the oximato‐bridged dinuclear complexes 9 , which were converted back to the chlorido complexes 6 upon treatment with an amine hydrochloride. In contrast, dehydrochlorination of 6 in 2‐propanol as well as the reaction of 9 with 2‐propanol yielded the hydrido‐bridged dinuclear oxime–oximato complexes 10 . Crossover experiments revealed that 10 dissociates into the mononuclear hydrido–oxime complex 11 and unsaturated oximato complex 12 , which are interconvertible by reactions with hydrogen donors and acceptors. Owing to the metal–ligand cooperation, 10 effectively catalyzed transfer hydrogenation of ketones with 2‐propanol.