A 2-iridafuran from reaction between a 1-iridaindene and methyl propiolate

The coordinatively unsaturated 1-iridaindene, Ir[C8H5(Ph-3)]Cl(PPh3)2 has a labile chloride ligand and is easily converted to the corresponding iodide, Ir[C8H5(Ph-3)]I(PPh3)2 (1) by reaction with NaI. When Ir[C8H5(Ph-3)]I(PPh3)2 (1) is treated with methyl propiolate a reactive five-coordinate complex with both a diphenylvinyl ligand from ring-opening of the 1-iridaindene, and a 3-methoxy-3-oxoprop-1-ynyl ligand from deprotonation of methyl propiolate, is first produced. Reaction of this complex with aqueous HCl generates the 2-iridafuran, Ir[OC3H(CHCPh2-3)(OMe-5)]ClI(PPh3)2 (2) probably from initial protonation at the β-carbon of the 3-methoxy-3-oxoprop-1-ynyl ligand to form a vinylidene ligand and subsequent migration of the diphenylvinyl ligand to the α-carbon of this ligand accompanied by oxygen coordination to iridium. Similar treatment of 1 with methyl propiolate followed by aqueous HI gives the corresponding complex, Ir[OC3H(CHCPh2-3)(OMe-5)]I2(PPh3)2 (3). The X-ray crystal structures of 2 and 3 together with NMR spectroscopic data confirm the 2-metallafuran structures of these complexes.

The 2-iridafuran, 3, results from reaction of the 1-iridaindene, 1, first with methyl propiolate and secondly with HI. The reaction proceeds through an initial ring-opening of the iridaindene by the methyl propiolate.Figure optionsDownload as PowerPoint slide