Chiral ruthenium(IV)-oxo complexes. Structure, reactivities of [Ru(terpy)(N∩N)O]2+ (N∩N = N,N,N′,N′-tetramethyl-1,2-diaminocyclohexane) and [Ru(Me3tacn)(cbpy)O]2+ (cbpy = (-)-3,3′-[(4S-trans)-1,3-dioxolane-4,5-dimethyl]-2,2′-bipyridine)