Remote Chirality Transfer within a Coordination Sphere by the Use of a Ligand Possessing a Concave Cavity

The possibility to enhance the effect of a modest chiral element in a metal ligand by the use of a second ligand possessing a concave cavity has been examined for the examples of 1,3- and 1,4-chirality transfer within the metal coordination sphere. Complexation of Ru(C₆₀Me₅)Cl(CO)₂ with (R)-prophos [(R)-1,2-bis(diphenylphosphino)propane] took place with excellent diastereoselectivity to give a configurationally stable chiral-at-metal complex, Ru(C₆₀Me₅)Cl((R)-prophos). This complex was converted, with good to perfect diastereoselectivity, into a variety of cationic complexes, [Ru(C₆₀Me₅)((R)-prophos)L][SbF₆] (L = MeCN, ^tBuCN, methacrolein, acetone, CO, BnNC, 2,6-Me₂C₆H₃NC), and a vinylidene complex, [Ru(C₆₀Me₅)(CCPhH)((R)-prophos)][SbF₆]. The chirality transfer to the reactants reacting in the outer sphere of the coordination resulted in an asymmetric Diels−Alder reaction, albeit with modest selectivity.