Syntheses and crystallographic studies of [Ir(η5-C5Me5)(L)(RF)I] (L = CO, PMe3; RF = CF2CF3, CF2CF2CF3, CF2C6F5, CF(CF3)2) complexes. Cone and solid angle steric parameters for perfluoroalkyl ligands

Abstract

Oxidative addition of R_FI (R_F = CF₂CF₃, CF₂CF₂CF₃, CF₂C₆F₅, CF(CF₃)₂) to [Ir(η⁵-C₅Me₅)(CO)₂] gave the iridium(III) complexes, [Ir(η⁵-C₅Me₅)(CO)(R_F)I] 2a–d in good yield. Carbonyl substitution by PMe₃ to give [Ir(η⁵-C₅Me₅)(PMe₃)(R_F)I] 3a–d was achieved by heating in refluxing toluene. Complexes 2a,c,d and 3a,b,d were studied by X-ray crystallography. The perfluoroalkyl Ir–C bonds were found to be shorter than alkyl Ir–C bonds, while the α-C–F bonds were longer than the C–F bonds in non-coordinated perfluorocarbons. The steric sizes of the perfluoroalkyl ligands were determined as Tolman cone angles, θ, and solid angles, Ω. The sizes of the ligands followed the expected trend, CF(CF₃)₂ > CF₂C₆F₅ > CF₂CF₂CF₃ ≈ CF₂CF₃, and were substantially larger than corresponding hydrocarbons.