Iridium(III)–vinylidene chemistry: Conversion of an iridacyclopentadiene-chlorido complex and terminal alkynes to iridacyclopentadiene–vinyl complexes

The reactions of [κ2(C1,C4)-CRCRCRCR](PPh3)2Ir(Cl) (9, R = CO2Me) with propargyl alcohol derivatives (2-propyn-1-ol, 2-methyl-3-butyn-2-ol, 1-ethynylcyclopentanol, and 1-ethynylcyclooctanol), in the presence of water leads to the formation of iridium(III)–vinyl complexes bearing the general structure [κ2(C1,C4)-CRCRCRCR](PPh3)2Ir(CO)(κ1-vinyl) where vinyl = –CHCH2, -(E)-CHCHMe, –CHC(CH2)4, or –CHC(CH2)7. In these, the CO ligand was derived from the terminal carbon of the starting alkyne and the oxygen atom from water. Under anhydrous conditions, 9 undergoes reaction with 2-propyn-1-ol to give trimethyl 1,3-dihydro-3-oxo-4,5,6-isobenzofurantricarboxylate, the result of a cycloaromatization/transesterification involving the buta-1,3-dien-1,4-diyl ligand in 9 and 2-propyn-1-ol.