Iridapyrrole Complexes via Formal 3 + 2 Cycloaddition of Iridium Alkenyls to Acetonitrile

Under appropriate conditions, the bis(ethylene) derivative Tp*Ir(C2H4)(2) (TP* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate) reacts with MeCN to provide the Ir(III) complex Tp*Ir(CH=CH2)(C2H5)(NCMe) (1). In the presence of catalytic amounts of water, 1 undergoes intramolecular coupling of the vinyl and acetonitrile ligands, with formation of a compound (2a) that contains a delocalized, five-membered iridapyrrole ring. This unusual cycloaddition reaction can be extended to other related alkenyl complexes of iridium.