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]

The diphenylallenylidene complexes [Ru( C C CPh 2 )(η 5 -C 9 H 7 )L 2 ][PF 6 ] (L = PPh 3; L 2 = 1,2-bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm)) ( 1 a − c ) react with NaOMe to yield the methoxyalkynyl derivatives [Ru{C⋮CC(OMe)Ph 2 }(η 5 -C 9 H 7 )L 2 ] ( 3 a − c ). Protonation of these species gives back the starting allenylidene derivatives. Regioselective additions on the C γ are also observed when 1 a, b are treated with LiR (R = Me, n Bu), giving the alkynyl complexes [Ru{C⋮CC(R)Ph 2 }(η 5 -C 9 H 7 )L 2 ] ( 4a, b, 5 a, b ). Vinylidene derivatives [Ru{ C C(H)C(R)Ph 2 }(η 5 -C 9 H 7 )(PPh 3 ) 2 ][BF 4 ] ( 6a, 7a ) can be prepared by protonation of complexes 4a and 5a with HBF 4 . The diphenylallenylidene compound 1c reacts with Li t Bu to yield the metallacycle ( 8c ). The alkynyl complexes [Ru{C⋮CC(C⋮CR)Ph 2 }(η 5 -C 9 H 7 )(PPh 3 ) 2 ] (R = Ph, n Pr, H) ( 9a − 11a ) have been obtained by reaction of 1a with lithium or sodium acetylides. Protonation of these derivatives yields the vinylidene complexes [Ru{ C C(H)C(C⋮CR)Ph 2 }(η 5 -C 9 H 7 )(PPh 3 ) 2 ][BF 4 ] ( 12a − 14a ). The crystal structure of [Ru{C⋮CC(C⋮CH)Ph 2 }(η 5 -C 9 H 7 )(PPh 3 ) 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{ C C C(H)Ph}(η 5 -C 9 H 7 )(PPh 3 ) 2 ][PF 6 ] ( 2a ) reacts with PMe 3, PMe 2 Ph, PMePh 2, and PPh 3 to yield the cationic alkynyl−phosphonio derivatives [Ru{C⋮CC(PR 3 )(H)Ph}(η 5 -C 9 H 7 )(PPh 3 ) 2 ][PF 6 ] ( 17a − 20a ) in a regioselective way. Similarly, allenylidene complexes 1 a − c add PMe 3 to give the corresponding alkynyl−phosphonio derivatives 15 a − c . [Ru{C⋮CC(PMe 3 )Ph 2 }(η 5 -C 9 H 7 )(dppm)][PF 6 ] ( 15c ) undergoes an isomerization process to yield the thermodynamically more stable allenyl−phosphonio complex [Ru{C(PMe 3 ) C CPh 2 }(η 5 -C 9 H 7 )(dppm)][PF 6 ] ( 21c ). [Ru{C(PMe 2 Ph) C CPh 2 }(η 5 -C 9 H 7 )(dppm)][PF 6 ] ( 22c ) can be obtained directly by addition of PMe 2 Ph to the C α atom of 1c . The behavior of the diphenylallenylidene complexes 1 a − c toward sodium 2-methylthiophenolate is also discussed.