Indenyl–ruthenium(ii) allenylidene complexes containing terpenic substituents as precursors of optically active terminal alkynes: scope and limitations†
Abstract
The optically active allenylidene complex [Ru{CCC(C9H16)}(η5-C9H7)(PPh3)2][PF6]
(C(C9H16)
=
(1R,4S)-1,3,3-trimethyl-bicyclo[2.2.1]hept-2-ylidene)
1 regio- and stereoselectively reacts with unhindered anionic nucleophiles to yield the neutral σ-alkynyl derivatives [Ru{CCC(C9H16)R}(η5-C9H7)(PPh3)2]
(R = H 2a, CN 2b, Me 2c, CCPh 2d). Protonation of 2a–d with HBF4·Et2O affords the cationic vinylidene complexes [Ru{CC(H)C(C9H16)R}(η5-C9H7)(PPh3)2][BF4]
3a–d, which can be easily demetalated, by treatment with