Tetradentate bis-phosphine ligands (P(2)N(2) and P(2)S(2)) and their Rh(III), Ni(II) and (105)Rh complexes: X-ray crystal structures of trans-[RhCl(2)(L2)]PF(6), [Ni(L2)](PF(6))(2) and μ-O(2)SO(2)-[Ni(L5)](2)(PF(6))(2).