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Acetylacetonato(phosphane)iridium Complexes: Synthesis and Catalytic Activity in the Cyclization of Alkynoic Acids
Author(s) -
Geier Michael J.,
Vogels Christopher M.,
Decken Andreas,
Westcott Stephen A.
Publication year - 2010
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.201000655
Subject(s) - chemistry , iridium , catalysis , denticity , intramolecular force , medicinal chemistry , methylene , stereochemistry , organic chemistry , crystal structure
The iridium complex [Ir(acac)(η 2 ‐coe) 2 ] ( 1 ) has been easily prepared by the addition of Tl(acac) to a suspension of [Ir(μ‐Cl)(η 2 ‐coe) 2 ] 2 in hexane. Complex 1 has been characterized fully including an X‐ray diffraction study. It is moderately stable and is a useful precursor to a number of different acetylacetonato(phosphane)iridium complexes via addition of monodentate and bidentate phosphanes. Reactions proceeded at room temperature to give high yields of the desired square planar phosphane complexes [Ir(acac)(P)] ( 2 : P = 2 PPh 3 , 3 : P = 2 PMePh 2 , 4 : P = dppm, 5 : P = dppe, 6 : P = dppp, 7 : P = dppb, 8 : P = dppf, 9 : P = dcpe) except for those involving dppe, which gave a complicated mixture of products. Complex [Ir(acac)(dppe)] ( 5 ) was prepared in a microwave reactor at 125 °C. All complexes prepared in this study were efficient in the intramolecular catalyzed cyclization of4‐pentynoic acid to give exclusive formation of the exocyclic γ‐methylene‐γ‐butyrolactone. Complex 1 was found to be the most active and selective catalyst precursor for the intramolecular cyclization of both 4‐pentynoic acid and 5‐hexynoic acid.