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(CCCPh2)(η5-C9H7)L2][PF6] (L = PPh3; L2 = 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)Ph2}(η5-C9H7)L2] (3 a−c). Protonation of these species gives back the starting allenylidene derivatives. Regioselective additions on the Cγ are also observed when 1 a,b are treated with LiR (R = Me, nBu), giving the alkynyl complexes [Ru{C⋮CC(R)Ph2}(η5-C9H7)L2] (4a,b, 5 a,b). Vinylidene derivatives [Ru{CC(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{CC(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{CCC(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 1 a−c add PMe3 to give the corresponding alkynyl−phosphonio derivatives 15 a−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)CCPh2}(η5-C9H7)(dppm)][PF6] (21c). [Ru{C(PMe2Ph)CCPh2}(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 1 a−c toward sodium 2-methylthiophenolate is also discussed.

Nucleophilic addition reactions to the allenylidene complex [Cp∗RuCCCPh2(CO)(PMeiPr2)]+: X-ray crystal structures of , , and

“…This suggests that the product resulting from the attack of the phosphine at C c is kinetic, and that the thermodynamically stable final product is always the allenylphosphonio derivative. Furthermore, it has been reported that the complex [(g 5 -Indenyl)Ru{C"CC(PMe 3 )Ph 2 }(dppm)] [PF 6 ] (dppm = 1,1-bis(diphenylphosphino)methane) undergoes an isomerization process to yield the thermodynamically more stable allenylphosphonio complex [(g 5 -Indenyl)Ru{C(PMe 3 )‚C‚CPh 2 }(dppm)][PF 6 ] [34]. As it has been previously observed for the alkynylphosphonio complex [Cp * Ru(C"CC(PEt 3 )Me 2 )(PEt 3 )]-[BPh 4 ] [33], complex 7 is also formed as by-product in many reactions involving the allenylidene complex 1, as a degradation product.…”

Extending the Chain: Synthetic, Structural, and Reaction Chemistry of a BN Allenylidene Analogue

“…While it is possible that steric factors play an important role in the observed selectivity, it is noteworthy that the corresponding reaction of the less encumbered para ‐tolyl derivative 4 a with Na[SPh] also proceeds exclusively by attack at boron. The regioselectivity of addition of thiophenolate reagents to related allenylidene complexes has been shown to be strongly dependent on the ancillary phosphine ligand set 17e. With regard to cyanide addition, α regiochemistry is also exhibited by 4 b ; this provides an interesting contrast with the γ‐selectivity observed towards CN − for systems of the type [(η 5 ‐C n H m )Ru(PPh 3 ) 2 (CCPh 2 )] + (C n H m =C 5 H 5 , C 9 H 7 ), in which the α center is presumably more sterically protected and also less electropositive (i.e.…”

Transition Metal Complexes of Neutral eta1-Carbon Ligands

“…Related processes have also been described starting from the chiral allenylidene [Ru( 5 - 6 ], allowing the preparation of propargylicsubstituted compounds with complete enantioselectivity [130]. 18) [113,265]. Although rare, regioselective nucleophilic additions of anions at the a-carbon of cationic ruthenium allenylidenes are also known, involving in all cases intramolecular processes.…”