Octahedral perfluoroalkyl complexes of Ir(III) formed by oxidative addition of perfluoroalkyl iodides to Ir(acac)(CO)₂

Abstract

Oxidative addition of primary, secondary, or benzylic perfluoroalkyl iodides (R F –I) to the phosphine free Ir(I) precursor Ir(acac)(CO)2 1 (acac = 2,4-pentanedionato) proceeds smoothly to afford octahedral Ir(III) products Ir(acac)(I)(R F )(CO) 2 , A combination of X-ray crystallographic studies and solution spectroscopy shows that these products are the result of overall trans-addition of the C–I bond to iridium, probably a result of thermodynamic control; evidence for a kinetic product resulting from net cis-addition is obtained in one case. Treatment of the Ir(III) compounds with AgOTf (Tf = CF 3 SO 3 ) illustrates that the iodo ligand is replaced by triflate with retention of stereochemistry at Ir. The resulting triflate complexes are inert to displacement by H 2 O or H 2 . The Ir(III) products exhibit very high CO stretching frequencies in the IR, indicating that the CO ligands may be non-classical. A quantitative estimation of the degree of backbonding to the CO ligands in these compounds, and a comparison of the π-acceptor properties of CO and fluoroalkyl ligands, is made using an approach based on Density Functional Theory (DFT) and Natural Bond Orbital analyses.Key words: iridium, fluoroalkyl, oxidation, carbonyl, DFT.