Chiral metal complexes. 26. Metal complexes of the new stereospecific tetraamine ligand 3R,4R- and 3S,4S-diphenyl-1,6-di(2-pyridyl)-2,5-diazahexane

The new N4 tetradentate 2,5-diaza-3,4-diphenyl-1,6-di(2-pyridyl)hexane (picstien), based on stilbenediamine, has been synthesised in its racemic and enantiomeric forms.R,R-Picstien coordinates to Co(III) to give the Λ-β[Co(R,R-picstien)Cl2]+ cation stereospecifically. This cation may be isolated as its chloride or perchlorate monohydrate salt using several different synthetic procedures, each of which yields products in several crops with identical NMR and chiroptical properties. The chloride donors in this cation undergo substitution by nitrite or oxalate with full retention of its Λ-β topology. A Rh(III) analogue of the dichloro complex also was isolated, and this has the same stereochemistry. The S,S antipode of the ligand was used to generate corresponding enantiomeric chelate forms.