THE STEREOCHEMISTRY OF THE OXIDATION OF DIAMINES AND OF THE REDUCTIONOF DIIMINES IN THE COORDINATION SPHERE OF RUTHENIUM(II)

The syntheses of Delta/Lambda-, Delta-, and Lambda-[Ru(bpy)(2)(1R,2R-c hxn)](2+) (where 1R,2R-chxn=(1R,2R)-(-)-1,2-diaminocyclohexane); rac.- , Delta-, and Lambda-[Ru(bpy)(2)(chxdiim](2+) (where chxdiim=1,2-diimi nocyclohexane); rac.-, and Delta-[Ru(bpy)(2)(dmen)](2+) (where dmen=N, N'-(dimethyl)ethylenediamine), and rac.-, and Delta-[Ru(bpy)(2)(dmdiim )](2+) (where dmdiim=N,N'-(dimethyl)ethylenediimine) are described. Ox idation of the coordinated diamines with an acid solution of Ce(IV) an d reduction of the coordinated diimines with NaBD4 occur under retenti on of the configuration at the metal center. Reduction of the diimine complexes with NaBD4 gives back the amines with a diastereomeric exces s (Lambda-R,R and Delta-S,S) of 60% in case of chxn as a ligand and 80 % for the dmen ligand. The latter becomes a chiral ligand upon deutera tion. The reduction also yields a small amount cup to 10%) of the corr esponding cis isomers (Delta-R,S/Lambda-S,R). In addition, semi-reduce d coordinated amine/imine ligands are observed as intermediates. The i dentity of the reaction products as well as their configurations has b een established by means of circular dichroism and H-1 NMR spectroscop y. (C) 1998 Elsevier Science S.A. All rights reserved.