Nucleophilic additions of anionic Group 6 carbene complexes on cationic indenyl–ruthenium(II) allenylidene derivatives: an easy entry to bimetallic complexes containing σ-alkynyl–carbene and vinylidene–carbene bridges †

Abstract

The novel indenyl–ruthenium(II) allenylidene complexes [Ru{CCC(R)Ph}(η5-C9H7)(PPh3)L][PF6] (L = PMePh2, R = Ph 4a, H 4b; L = PMe2Ph, R = Ph 5) have been prepared by reaction of [RuCl(η5-C9H7)(PPh3)L] (L = PMePh22, PMe2Ph 3) with HCCC(OH)(R)Ph and NaPF6 in methanol. These allenylidene derivatives as well as [Ru{CCC(R)Ph}(η5-C9H7)(PPh3)2][PF6] (R = Ph 1a, H 1b) undergo regioselective nucleophilic additions of anionic Fischer type carbene complexes [Li][(CO)5M{C(OMe)CH2}] (M = Cr, W, Mo) at the Cγ atom of the unsaturated chain to afford the neutral bimetallic σ-alkynyl derivatives [Ru(CCC(R)Ph{CH2C(OMe)M(CO)5})(η5-C9H7)(PPh3)L] (L = PPh3, R = Ph, M = Cr 6a, W 6b, Mo 6c; L = PPh3, R = H, M = Cr 7a, W 7b; L = PMePh2, R = Ph, M = Cr 8a, W 8b; L = PMePh2, R = H, M = Cr 9a, W 9b; L = PMe2Ph, R = Ph, M = Cr 10a, W 10b). Protonation of these derivatives with HBF4·Et2O yields cationic vinylidene complexes [Ru(CC(H)C(R)Ph{CH2C(OMe)M(CO)5})(η5-C9H7)(PPh3)L][BF4] 11a–c, 12–15a,b which represent the first examples of bimetallic species containing a vinylidene–carbene bridge. Heating under reflux solutions of vinylidene complexes 11b and 12b in acetonitrile affords the carbene derivatives [(CO)5W{C(OMe)CH2C(R)Ph(CCH)}] (R = Ph 16a, H 16b) and the nitrile complex [Ru(NCMe)(η5-C9H7)(PPh3)2][BF4] 17. The diphenylallenylidene complex 1a regioselectively reacts with NaCN to yield the σ-alkynyl derivative [Ru{CCCPh2(CN)}(η5-C9H7)(PPh3)2] 18. Treatment of 18 with one equivalent of [M(CO)5(THF)] leads to the formation of the bimetallic σ-alkynyl complexes [Ru(CCCPh2{CN–M(CO)5})(η5-C9H7)(PPh3)2] (M = Cr 20a, W 20b, Mo 20c).