Chiral ruthenium-allenylidene complexes that bear a fullerene cyclopentadienyl ligand: Synthesis, characterization, and remote chirality transfer

Ruthenium complexes that bear both a fullerene and an allenylidene ligand, [Ru(C60Me5)((R)-prophos) = C=C=(CRR2)-R-1]PF6 (prophos = 1,2-bis(diphenylphosphanyl)propane), were prepared by the reaction of [Ru(C60Me5)Cl((R)-prophos)] and a propargyl alcohol in better than 90% yields, and characterized by H-1, C-13, and P-31 NMR, IR, and UV/Vis/NIR spectroscopy and MS. Cyclic voltammograms of these complexes showed one reversible or irreversible reduction wave due to the allenylidene part, and two reversible reduction waves due to the fullerene core. Nucleophilic addition of RMgBr or RLi proceeded regioselectively at the distal carbon atom of the allenylidene array. The reaction took place with a 60:40-95:5 level of diastereoselectivity with respect to the original chirality in the (R)-prophos ligand, which is located six atoms away from the electrophilic carbon center.