CHIRAL ATROPISOMERIC 5-MEMBERED BIHETEROAROMATIC DIPHOSPHINES - NEW LIGANDS OF THE BIBENZIMIDAZOLE AND BIINDOLE SERIES

Two new chiral atropisomeric biheteroaromatic diphosphines are describ ed: 2,2'-bis(diphenylphosphino)-1,1'-bibenzimidazole (3a) and dimethyl -1,1'-bis(diphenylphosphino)-2,2'-biindole (4a) structural characteriz ation is given and configurational stability at room temperature demon strated. The oxidation potential was recognized as a good tool to eval uate the electronic availability of the phosphorus atom in the series of biheteroaromatic diphosphines. Its value increases parallel to the electronic demand of the heterocyclic system and also depends on the p osition of the diphenylphosphino group. (C) 1997 Elsevier Science S.A.