Metal complexes of a chiral quadridentate Schiff base

Chiral metal Schiff-base complexes [AlL(Et)], [TiLCl(2)], [VO(L)], [(FeL)(2)O], [CoL], [NiL], [CuL], [ZrLCl(2)], [RuL(CO)(2)] and trans-[RuL(NO)Cl] ([H(2)L = (R,R)-(-)-N,N'-bis(3,5-di-tert-butylsalicylidene)cyclohexane-1,2-diamine] were synthesized and characterized. The structures of [CoL] and trans-[RuL(NO)Cl] have been established by X-ray crystallography. The former has a pseudo-square-planar geometry with Co-N and Co-O distances of 1.88 and 1.84 Angstrom, respectively. The geometry around Ru in trans-[RuL(NO)Cl] is octahedral with Ru-N (nitrosyl) and Ru-Cl distances of 1.72(2) and 2.354(4) Angstrom, respectively, and Ru-N-O 175(2)degrees. The cyclic voltammograms for the metal Schiff-base complexes show reversible M(III)-M(II) and ligand-centred oxidation couples. Treatment of NIL with AgBF4 afforded air-stable [NIL]BF4, which is formulated as a nickel(Ir) complex of the Schiff-base cation radical.