The stereospecific synthesis of Λ-α-{dipyrido[3,2-a:2′3′-c](6,7,8,9-tetrahydro)phenazine[N,N′-di(2-picolyl)-2,5-dimethyl-2S,5S-diaminocyclohexane]ruthenium(ii)} and related β-isomers

Abstract

The conglomerate Δ,Λ-α-[Ru(picchxnMe₂)(dpqC)](ClO₄)₂·0.5H₂O and Λ-α-[Ru(S,S-picchxnMe₂)(dpqC)](ClO₄)₂·0.5H₂O (where picchxnMe₂ = N,N′-dimethyl-1,2-di(2′-picolyl)-S,S-diaminocyclohexane and dpqC = dipyrido[3,2-a:2′3′-c](6,7,8,9-tetrahydro)phenazine) have been isolated. Single crystal X-ray structures have been determined, although it was discovered only after initial data had been collected that the Δ,Λ-α-[Ru(picchxnMe₂)(dpqC)](ClO₄)₂·0.5H₂O species was in fact a conglomerate. Λ-α-[Ru(S,S-picchxnMe₂)(dpqC)](ClO₄)₂·0.5H₂O crystallises in the orthorhombic space group C222₁ with a = 15.127(2), b = 22.976(4), c = 25.561(7) Å, (alternatively a = 15.187(3), b = 23.003(6), c = 25. 685(7) Å, for the separate determination of a crystal of the conglomerate), Z = 8, and the Λ-α structure was refined to an R value of 0.059. This structure enables, for the first time, the correlation of the absolute configurations for Ru(II) complexes of the N₄ tetradentate with their CD spectra. We also report here a procedure to synthesise and isolate enantiomerically pure isomers of tetradentate metal complexes of the types α- and β-[Ru(R*,R*-picchxnMe₂)(dpqC)]²⁺.