Competition between vinylidene rearrangement and 1,2-insertion of carbon-disubstituted internal alkynes at a (CpIr)-Ir-star(III) complex

Competition between vinylidene rearrangement/1,1-insertion and 1,2-alkyne insertion into the Ir-Ar bond of [(CpIr)-Ir-star( ppy-F-4)](+) was observed on reaction with diarylacetylenes. The former process afforded the iridacycle 2 via the subsequent 1,4-Ir migration, whereas the latter led to the pyridoisoquinolinium complex 4. Detailed analysis revealed that 4 isomerizes to 2 by heating at 50 degrees C.