The first representative of 1,5-diaza-3,7-diphosphacyclooctanes (1) with chiral L-menthyl substituents on the phosphorus atoms was obtained by condensation of L-menthylphosphine with formaldehyde and p-toluidine. This optically active cyclic bisphosphine readily forms a stable PP-complex with borane (2) and P,P-chelate complexes with platinum(II) (3) and palladium(II) dichloride (4). The structure of the bisphosphine 1 in solution was elucidated by employing a variety of 1D/2D NMR correlation experiments, and the molecular structure of complex 3 was studied by X-ray crystallography.