Insertion of symmetric alkynes into the σ[Pd-C(sp ~2, ferrocene)] bond of palladacycles with [C(sp ~2, ferrocene),N, S(thienyl)] - pincer ligands

摘要

A study of the reactivity of [Pd({(η ~5-C _5H _3)-CH=N-(CH _2) _n-(C _4H _3S)}Fe{η ~5-C _5H _5})Cl], n = 2 (1e) or 1 (1f), with symmetric alkynes R ~1-C≡C-R ~1 (R ~1 = CO 2Me, Et or Ph) has allowed us to achieve the di-μ-chloro-bridged complexes [Pd({(MeO _2C-C=C-CO _2Me)(η ~5-C _5H _3)-CH=N-(CH _2) _n-(C _4H _3S)}Fe{η ~5- C _5H _5})μ-Cl] _2, n = 2 (3e) or 1 (3f), and the mononuclear derivatives [Pd({(MeO _2C-C=C-CO _2Me) (η ~5-C _5H _3)-CH=N-(CH _2) _n-(C _4H _3S)}Fe{η ~5-C _5H _5})Cl(PPh _3)], n = 2 (4e) or 1 (4f), [Pd({(R ~1-C=C-R ~1) _2(η ~5-C _5H _3)-CH=N-(CH _2) _n-(C _4H _3S)}Fe{η ~5-C _5H _5})Cl],R ~1 = CO _2Me, n = 2 (5e) or 1 (5f), R ~1 = Et, n = 2 (6e) or 1 (6f), or R ~1 = Ph, n = 2 (7e), and [Pd({(Ph-C=C-Ph) _2(η ~5-C _5H _3)-CH=N-(CH _2)-(C _4H _3S)} Fe{η ~5-C _5H _5})Cl(PPh _3)] (7f·1/2Ph-≡C-Ph). With MeO _2C-C≡C-CO 2Me, mono- (3e, 3f, 4e and 4f) and bis-insertion complexes (5e and 5f) were obtained, whereas for R ~1-C≡C-R ~1 with R ~1 = Et or Ph, only bis-insertion products (6e, 6f, 7e and 7f) were isolated. These studies also proved that 1e and 1f, which have a labile Pd-S(thienyl) bond, are more prone to undergo the insertion of R ~1-C≡C-R ~1 (R ~1 = CO _2Me, Et or Ph) than their analogues with [C(sp 2,ferrocene), N, X] - [X = O, N(amine) or S(thioether)] pincer ligands.