Diphosphines of a mixed heteroarylic-arylic type, wherein the phosphine group carrying backbone is constituted by the interconnection of a five-atom heteroaromatic ring and a carbocyclic aromatic ring, forming an atropoisomeric chiral system with a C.sub.1 symmetry. Said chiral diphosphines are advantageously used as ligands for the formation of chiral complexes with transition metals, in particular Ru, Rh, Pd, Ir, Ni. The so-obtained chiral complexes are used as chiral complexes are used as chiral catalysts for stereocontrolled reactions, in particular diastereo and enantioselective reduction reactions, hydroformylation reactions, hydrosilylation reactions, hydrocyanation reactions, double-bond isomerisation reactions, other reactions of carbon--carbon bond formation.