Ring slip in associative reactions of some indenyl and phenylcyclopentadienyl iridium complexes

Article abstract of DOI:10.1021/om00107a016

The complex ion [(η⁵-Ind)IrHL₂]⁺ (Ind = indenyl, L = PPh₃) undergoes substitution with t-BuNC, CO, and PMe₃, while the Cp analogue (Cp = cyclopentadienyl) is inert. The phenylcyclopentadienyl complex [(η⁵-PhC₅H₄)IrHL₂]⁺ undergoes rapid substitution with PMe₃ but not with t-BuNC or CO. Slipped η³ and η¹ intermediates are proposed in these reactions, and several examples of such complexes are detected by NMR at low temperatures. Deprotonation with n-BuLi takes place only for [(η⁵-Ind)IrHL₂]⁺ and [(η⁵-PhC₅H₄)IrHL₂]⁺, but not the Cp analogue. The reactions of the deprotonated complex [(η⁵-Ind)IrL₂] with a number of electrophiles are also investigated and the resulting cations [(η⁵-Ind)IrXL₂]⁺ (X = Me, Et, CH₂Ph, Cl, I) characterized. The ethyl complex loses ethylene at 60°C by β-elimination, but only in donor solvents, which may attack associatively in the first step of the reaction. In nondonor solvents, the β-elimination is induced by UV photolysis, which may induce ring slip. Allyl bromide reacts with [(η⁵-Ind)IrL₂] to give [(η⁵-Ind)Ir(η³-allyl)L]⁺, via [(η⁵-InD)Ir(η¹-allyl)L₂]⁺ as an observed but unisolated intermediate. The structure of the chloro complex [(η⁵-Ind)IrClL₂] was determined by X-ray methods (space group P1; a = 11.314 (4) A?, b = 14.469 (5) A?, c = 13.021 (2) A?, a = 87.05 (2)°, β = 100.25 (2)°, γ = 68.43 (2)°; V = 1934.8 (10) A?³; mol wt = 954.2, Z = 2; F(000) = 944; ρ_calcd = 1.638 g cm^-3; R = 0.04 for 6379 reflections). Hydrogenation of [(η⁵-Ind)IrHL₂]⁺ with Rh/C gives the tetrahydroindenyl complex.