An Unprecedented Type of Insertion of an Alkyne into a Metal−Carbon Bond

Treatment of the (allenylidene)iridium complex trans-[IrCl(CCCPh2)(PiPr3)2] (1) with KOH
leads to trans-[Ir(OH)(CCCPh2)(PiPr3)2] (2), which
reacts with Brønsted acids such as HF and phenol to
give trans-[IrF(CCCPh2)(PiPr3)2] (3) and trans-[Ir(OPh)(CCCPh2)(PiPr3)2] (4). Moreover, an unusual
reaction of 2 with excess alkynes RC⋮CH (R = Ph, CO2Me) takes place to afford trans-[Ir(C⋮CR)2{(E)-CHCRCHCCPh2}(PiPr3)2] (5, 6). Compounds 3 and 5
were characterized by X-ray structure analysis.