Regioselective Nucleophilic Additions on Indenyl−Ruthenium(II)−Allenylidene Complexes. X-ray Crystal Structure of the Alkynyl Complex [Ru{C⋮CC(C⋮CH)Ph₂}(η⁵-C₉H₇)(PPh₃)₂]

Abstract

The diphenylallenylidene complexes [Ru(CCCPh2)(η5-C9H7)L2][PF6] (L = PPh3; L2 = 1,2-bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm)) (1a−c) react with NaOMe to yield the methoxyalkynyl derivatives [Ru{C⋮CC(OMe)Ph2}(η5-C9H7)L2] (3a−c). Protonation of these species gives back the starting allenylidene derivatives. Regioselective additions on the Cγ are also observed when 1a,b are treated with LiR (R = Me, nBu), giving the alkynyl complexes [Ru{C⋮CC(R)Ph2}(η5-C9H7)L2] (4a,b, 5a,b). Vinylidene derivatives [Ru{CC(H)C(R)Ph2}(η5-C9H7)(PPh3)2][BF4] (6a, 7a) can be prepared by protonation of complexes 4a and 5a with HBF4. The diphenylallenylidene compound 1c reacts with LitBu to yield the metallacycle (8c). The alkynyl complexes [Ru{C⋮CC(C⋮CR)Ph2}(η5-C9H7)(PPh3)2] (R = Ph, nPr, H) (9a−11a) have been obtained by reaction of 1a with lithium or sodium acetylides. Protonation of these derivatives yields the vinylidene complexes [Ru{CC(H)C(C⋮CR)Ph2}(η5-C9H7)(PPh3)2][BF4] (12a−14a). The crystal structure of [Ru{C⋮CC(C⋮CH)Ph2}(η5-C9H7)(PPh3)2] (11a) was determined by X-ray diffraction methods. In the structure the alkynyl chain is nearly linear (Ru−C(1)−C(2) = 175.0(2)°) with Ru−C(1) and C(1)−C(2) distances of 1.993(2) and 1.209(3) Å, respectively. The monosubstituted allenylidene complex [Ru{CCC(H)Ph}(η5-C9H7)(PPh3)2][PF6] (2a) reacts with PMe3, PMe2Ph, PMePh2, and PPh3 to yield the cationic alkynyl−phosphonio derivatives [Ru{C⋮CC(PR3)(H)Ph}(η5-C9H7)(PPh3)2][PF6] (17a−20a) in a regioselective way. Similarly, allenylidene complexes 1a−c add PMe3 to give the corresponding alkynyl−phosphonio derivatives 15a−c. [Ru{C⋮CC(PMe3)Ph2}(η5-C9H7)(dppm)][PF6] (15c) undergoes an isomerization process to yield the thermodynamically more stable allenyl−phosphonio complex [Ru{C(PMe3)CCPh2}(η5-C9H7)(dppm)][PF6] (21c). [Ru{C(PMe2Ph)CCPh2}(η5-C9H7)(dppm)][PF6] (22c) can be obtained directly by addition of PMe2Ph to the Cα atom of 1c. The behavior of the diphenylallenylidene complexes 1a−c toward sodium 2-methylthiophenolate is also discussed.