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2,5‐Norbornadiene C–C Coupling Reactions Mediated by Iridium Complexes
Author(s) -
Betoré M. Pilar,
Casado Miguel A.,
GarcíaOrduña Pilar,
Lahoz Fernando J.,
Polo Víctor,
Oro Luis A.
Publication year - 2016
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.201600336
Subject(s) - chemistry , norbornadiene , iridium , metallacycle , molecule , stereochemistry , ammonia , cyclooctadiene , adduct , medicinal chemistry , crystallography , x ray crystallography , catalysis , organic chemistry , physics , diffraction , optics
The treatment of [{Ir(µ‐Cl)(cod)} 2 ] (cod = 1,5‐cyclooctadiene) with 2,5‐norbornadiene (nbd) in the presence of triethylphosphane under an atmosphere of ammonia afforded the cation complex [Ir(κ C ,κ C ‐C 21 H 24 )(NH 3 ) 3 (PEt 3 )]Cl ( 1a ) and complex [Ir(κ C ,κ C ‐C 21 H 24 )Cl(NH 3 ) 2 (PEt 3 )] ( 1b ), the structures of which include a novel seven‐membered iridacycle formed by three half‐coupled nbd molecules. The formation of the metallacycle has been found to occur through several steps. First, the nbd displaces the cod in [{Ir(µ‐Cl)(cod)} 2 ] to give the Ir III chloro‐bridged complex [{Ir(κ C ,κ C ‐C 14 H 16 )(µ‐Cl)(η 4 ‐C 7 H 8 )} 2 ] ( 2 ), which bears a η 4 ‐ C=C ‐coordinated nbd and a five‐membered iridacycle formed by two half‐coupled nbd moieties. Further reaction with PEt 3 induces the C–C coupling between the iridacycle and the coordinated nbd to give the chloro‐bridged complex [{Ir(κ C ,κ C ‐C 21 H 24 )(µ‐Cl)(PEt 3 )} 2 ] ( 4 ). Finally, 4 reacts with gaseous ammonia to split the chloro bridges and form species 1a and 1b . Also, complex 2 was found to react with several donor ligands to afford the corresponding mononuclear adducts [Ir(κ C ,κ C ‐C 14 H 16 )Cl(η 4 ‐C 7 H 8 )(L)] [L = py ( 5 ), NH 3 ( 6 ), PMe 2 Ph ( 7 ), t BuNC ( 8 )]. The X‐ray molecular structures of 5 , 7 and 8 show the presence of a five‐membered iridacycle, but their stereochemistries differ by virtue of the relative locations of the respective added ligand.