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

TThe novel indenyl-ruthenium(II) allenylidene complexes [Ru{=C=C=C(R)Ph}(eta(5)-C9H7)(PPh3)L][PF6] (L = PMePh2, R = Ph 4a, H 4b; L = PMe2Ph, R = Ph 5) have been prepared by reaction of [RuCl(eta(5)-C9H7)(PPh3)L] (L = PMePh2 2, PMe2Ph 3) with HC=CC(OH)(R)Ph and NaPF6 in methanol. These allenylidene derivatives as well as [Ru{=C=C=C(R)Ph}( eta(5)-C9H7)(PPh3)(2)][PF6] (R = Ph 1a, H 1b) undergo regioselective nucleophilic additions of anionic Fischer type carbene complexes [Li][(CO)(5)M{=C(OMe)CH2}] (M = Cr, W, Mo) at the C atom of the unsaturated chain to a ord the neutral bimetallic sigma-alkynyl derivatives [Ru(C=CC(R)Ph{CH2C(OMe)=M(CO)(5)})(eta(5)-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(=C=C(H)C(R)Ph{CH2C(OMe)=M(CO)(5)})(eta(5)-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)(5)W{=C(OMe)CH2C(R)Ph(C=CH)}] (R = Ph 16a, H 16b) and the nitrile complex [Ru(N=CMe)(eta(5)-C9H7)(PPh3)(2)][BF4] 17. The diphenylallenylidene complex 1a regioselectively reacts with NaC=N to yield the sigma-alkynyl derivative [Ru{C=CCPh2(C=N)}(eta(5)-C9H7)(PPh3)(2)] 18. Treatment of 18 with one equivalent of [M(CO)(5)(THF)] leads to the formation of the bimetallic sigma-alkynyl complexes [Ru(C=CCPh2{C=N-M(CO)(5)})(eta(5)-C9H7)(PPh3)(2)] (M = Cr 20a, W 20b, Mo 20c).