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Acetonitrile Coupling at an Electron‐Rich Iridium Center Supported by a PC sp 2 P Pincer Ligand
Author(s) -
Burford Richard J.,
Piers Warren E.,
Parvez Masood
Publication year - 2013
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.201300152
Subject(s) - chemistry , heterolysis , acetonitrile , iridium , pincer ligand , pincer movement , ligand (biochemistry) , carbene , moiety , photochemistry , medicinal chemistry , bridging ligand , crystallography , stereochemistry , crystal structure , organic chemistry , receptor , catalysis , biochemistry
Aryl amido iridium complexes supported by a tridentate phosphanyl–carbene–phosphanyl pincer ligand [(PC sp 2P)Ir–N(H)Ar, Ar = C 6 H 5 , 1a ; Ar = 2,6‐ i Pr 2 C 6 H 3 , 1b ] react with acetonitrile to afford the dimeric complex 2 , in which two (PC sp 2P)Ir fragments are bridged by a diiminato ligand derived from two molecules of CH 3 CN. Metrical parameters obtained from X‐ray structural determination of 2 confirm that the bridging ligand is a diiminato species rather than an enediamido moiety, which indicates that the reductive coupling is mediated by one electron per iridium center. Experiments suggest that the reaction proceeds by heterolytic cleavage of the Ir–N(H)Ar bond followed by one‐electron reduction of the resulting Ir I –NCCH 3 cation by the amido anion. The resulting anilino radical rapidly abstracts a hydrogen atom from the solvent. The reductive coupling of acetonitrile at a late transition metal center is unusual and in this instance occurs as a result of the highly σ‐donating, electron‐rich nature of the PC sp 2P ligand.