Reaction of alkenes with trans-MeOIr(CO)(PPh₃)₂. Crystal and molecular structure of the pentacoordinate alkoxy-alkene iridium(I) complex, MeOIr(CO)(PPh₃)₂(TCNE)

The reaction of trans-MeOIr(CO)(PPh₃)₂ with TCNE (tetracyanoethylene) gives rise to the stable adduct MeOIr(CO)(PPh₃)₂(TCNE), the structure of which has been determined via a single-crystal X-ray diffraction study. This complex crystallizes in the centrosymmetric orthorhombic space group Pbca (D¹⁵_2h; No. 61) with a 17.806(4), b 20.769(4), c 20.589(6) Å, V 7614(3) ų and Z = 8. Diffraction data (Mo-K_α, 2θ = 5-45°) were collected on a Syntex P2₁ automated four-circle diffractometer and the structure was solved and refined to R_F 6.2% for 3502 data with |F₀| > 3σ(|F₀|) (R_F 4.3% for those 2775 data with |F₀| > 6 σ(|F₀|)). The central iridium atom has a distorted trigonal bipyramidal coordination geometry in which the methoxy group (Ir-OMe 2.057(8) Å) and carbonyl ligand (Ir-CO 1.897(14) Å) occupy axial sites with ∠MeOIrCO 174.7(4)°. The two triphenylphosphine ligands occupy equatorial sites (IrP(1) 2.399(3), IrP(2) 2.390(3) Å, ∠P(1)IrP(2) 110.32(11)° and the TCNE ligand is linked in an η² "face-on" fashion with the olefinic bond parallel to the equatorial coordination plane (IrC(4) 2.176(10), IrC(7) 2.160(12) Å) and lengthened substantially from its value in the free olefin (C(4)C(7) 1.539(17) Å).