Phosphonioalkynyl indenylruthenium(II) complexes [Ru{CCC(R)H(PR3)}(η5-C9H7)(PPh3)2][PF6] (R = Ph, PR3 = PMe3; R = H, PR3 = PPh3): suitable precursors of highly unsaturated σ-alkynyl and vinylidene derivatives

Abstract

Deprotonation of the phosphonioalkynyl ruthenium(II) complexes [Ru{CCC(R¹)H(PR₃)}(η⁵-C₉H₇)(PPh₃)₂][PF₆] (R¹ = Ph, PR₃ = PMe₃ 1; R¹ = H, PR₃ = PPh₃ 2) with LiBuⁿ in THF at –20 °C gave the ylide alkynyl derivatives [Ru{CCC(R¹)PR₃}(η⁵-C₉H₇)(PPh₃)₂] (R¹ = Ph, PR₃ = PMe₃ 3; R¹ = H, PR₃ = PPh₃ 4), which react in situ with aldehydes or ketones via a Wittig process to afford the neutral σ-enynyl complexes [Ru{CCC(R¹)CR²R³}(η⁵-C₉H₇)(PPh₃)₂] [R²R³ = CH₂(CH₂)₃CH₂, R¹ = Ph 5a or H 6a; R² = H, R³ = Me, R¹ = Ph 5b or H 6b; R² = R³ = R¹ = Ph 5c]. Compounds 5b and 6b have been obtained as mixtures of the corresponding E and Z stereoisomers. Protonation of 5 and 6 with HBF₄·Et₂O in THF at –20 °C takes place selectively on the C_β of the enynyl chain to yield the cationic vinylvinylidene derivatives [Ru{CC(H)C(R¹)CR²R³}(η⁵-C₉H₇)(PPh₃)₂][BF₄] [R²R³ = CH₂(CH₂)₃CH₂, R¹ = Ph 7a or H 8a; R² = H, R³ = Me, R¹ = Ph 7b or H 8b; R² = R³ = R¹ = Ph 7c]. The σ-polyenynyl complexes [Ru{CCC(R¹)CH(CHCH)_nR²}(η⁵-C₉H₇)(PPh₃)₂] (n = 1, R² = Ph, R¹ = Ph 9a or H 10a; R² = Prⁿ, R¹ = Ph 9b or H 10b; n = 2, R² = Me, R¹ = Ph 11 or H 12) have been obtained in high yields, as mixtures of the E and Z stereoisomers, by reaction of 3 and 4 with unsaturated aldehydes. Protonation of these derivatives yielded the highly unsaturated vinylidene complexes [Ru{CC(H)C(R¹)CH(CHCH)_nR²}(η⁵-C₉H₇)(PPh₃)₂][BF₄] (n = 1, R² = Ph, R¹ = Ph 13a or H 14a; R² = Prⁿ, R¹ = Ph 13b or H 14b; n = 2, R² = Me, R¹ = Ph 15 or H 16). The σ-ynenynyl and σ-keteniminyl complexes [Ru{CCC(Ph)CH(CCPh)}(η⁵-C₉H₇)(PPh₃)₂] and [Ru{CCC(Ph)CNPh}(η⁵-C₉H₇)(PPh₃)₂] have also been prepared by reaction of 3 with PhCCCHO and phenyl isocyanate, respectively. The ¹H, ³¹P-{¹H} and ¹³C-{¹H} NMR data for all the novel complexes are reported.