2,5-norbornadiene C–C coupling reactions mediated by iridium complexes

The treatment of [{Ir(µ-Cl)(cod)}] (cod = 1,5-cyclooctadiene) with 2,5-norbornadiene (nbd) in the presence of triethylphosphane under an atmosphere of ammonia afforded the cation complex [Ir(κC,κC-CH)(NH)(PEt)]Cl (1a) and complex [Ir(κC,κC-CH)Cl(NH)(PEt)] (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)}] to give the Irchloro-bridged complex [{Ir(κC,κC-CH)(µ-Cl)(η-CH)}] (2), which bears a η-C=C-coordinated nbd and a five-membered iridacycle formed by two half-coupled nbd moieties. Further reaction with PEtinduces the C–C coupling between the iridacycle and the coordinated nbd to give the chloro-bridged complex [{Ir(κC,κC-CH)(µ-Cl)(PEt)}] (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(κC,κC-CH)Cl(η-CH)(L)] [L = py (5), NH(6), PMePh (7), tBuNC (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.The authors express their appreciation for the financial supportby the Spanish Ministerio de Economía y Competitividad/Fondos Europeos para el Desarrollo Regional (MINECO/FEDER)(project CTQ2015-67366-P) and Diputación General de Aragón(group E07) (DGA/FSE-E07). Support from KFUPM – Universityof Zaragoza, Spain and the Centre of Research Excellence inPetroleum Refining & Petrochemicals (KFUPM), Zaragoza, Spainis gratefully acknowledged.Peer Reviewe