Optically active complexes of Schiff bases. Part 4. An analysis of the circular-dichroism spectra of some complexes of different co-ordination numbers with quadridentate Schiff bases of optically active diamines

The circular dichroism (c.d.) spectra of some transition-metal complexes of quadridentate Schiff bases derived from the condensation of 2 mol of salicylaldehyde with optically active (+)-(S)-propylene-1,2-diamine, (+)-(SS)-butane-2,3-diamine, trans-(+)-(SS)-cyclohexane-1,2-diamine, (+)-(S)-1 -phenylethylenediamine, and (–)-(SS)-1,2-diphenylethylenediamine are reported. The conformational behaviour of the diamine chelate ring is discussed in relation to the co-ordination number of the metal ion (M = VIV, FeIII, CoII, CoIII, NiII, or CuII). The assignment of the SS absolute configuration to (–)-1,2-diphenylethylenediamine has been confirmed. The anomalies in the c.d. spectra of metal complexes of Schiff bases containing this diamine are discussed.