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)

Abstract

The complexes [RuIV(terpy)(cxhn)O](ClO4)2 (cxhn = N,N,N′,N′-tetramethyl-1,2-diaminocyclohexane, terpy = 2,2′:6′,2″(terpyridine) and RuIV(Me3tacn)(cbpy)O](ClO4)2 (cbpy = (-)-3,3′-[(4S-trans)-1,3-dioxolane-4,5-dimethyl]-2,2′-bipyridine and Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) have been prepared and crystal structures of [RuIV(terpy)(cxhn)O](ClO4)2 and [RuII(Me3tacn)(3,3′-Me2bpy)(OH 2)](ClO4)2 have been determined [RuIV(terpy)(cxhn)O](ClO4)2 H2O, C25H35Cl2N5O10Ru, Mr = 737.68, space group P21ln, monoclinic, a = 8.215(5), b = 14.650(7), c = 24.261(10) Å, β = 94 78(4)°, Z = 4, [RuII(Me3tacn)(3,3′-Me2bpy)(OH 2)](ClO4)2, C21H35Cl2N5O9Ru, Mr = 673.52, space group P21ln, monoclinic, a = 8.463(1), b = 10.751(1), c = 30.192(3) Å, β = 91.77(1)°, Z = 4. The Ru=O distance in [RuIV(terpy)(cxhn)O](ClO4)2 is 1.827(14) Å. All the ruthenium-oxo complexes react with alkenes to give the corresponding epoxides. Stoichiometric oxidation of styrene and 4-chlorostyrene by [RuIV(terpy)(1R,2R-cxhn)O](ClO4)2 gave the corresponding epoxide with no enantiomeric excess. Using [RuIV(Me3tacn)(cbpy)O](ClO4)2, a 9% enantiomeric excess of R-styrene oxide and R-4-chlorostyrene oxide were found in the oxidation of both styrene and 4-chlorostyrene, respectively.