Hydridophosphoranes, which can be prepared by an exchange reaction involving alcoholysis or aminolysis of the P-III-OR or p(III)-NR2 bonds,(1) have aroused interest as ligands for reactive metal complexes.(2) Riess and co-workers(3) have focused on the coordination of bicyclophosphoranes, whereas Lattman and co-workers(4) have been interested in the complexation of tetracyclic cyclen- and cyclamphosphoranes. To our knowledge, chiral bicyclic or tetracyclic hydridophosphoranes have not yet been used for the synthesis of chiral organophosphorus ligands coordinated to a metal center.(5) We previously reported the synthesis of a new class of chiral tricyclic phosphoranes, the "triquinphosphoranes", from chiral enantiopure diaminodiols that present a C-2 symmetry axis.(6) We showed that these phosphoranes exist as two trigonal bipyramid structures (TBP) with opposite absolute configurations at the phosphorus atom, R-P and S-P, in a fast equilibrium by a Berry pseudorotation process (Scheme 1).(6b,7) We also described the first asymmetric addition of chiral triquinphosphorane 1a to ketopantolactone and to BH3. SMe2 complex leading to chiral alkoxyphosphorane 2 and chiral triquinphosphorane-borane adduct 3, respectively (Scheme 2).(6) The X-ray diffraction structures of 2(8) and 3(6b) revealed that the pentacoordinated structure is retained with a deformation percentage of 66 and 6.9%, respectively, along the Barry coordinate from the ideal TBP (0%) toward the ideal SP (100%). As the X-ray structure of 3 showed, the borane group coordinated to the axial nitrogen atom of the TBP structure is in syn position with respect to the P-H bond and in anti position with respect to the adjacent pseudoaxial isopropyl substituent.(6b) Recently, Gavrilov et al. reported the first example in which triquinphosphorane Ib (R = Et, R'= H) coordinates to platinum (TI) [Pt(COD)Cl-2] as the phosphoranide, based on P-31 NMR data. At 60 degrees C, a ring opening in the phosphorane structure leads to a new Pt-II complex in which both the oxazaphospholidine phosphorus pm and the amine nitrogen atoms coordinate the Pt-II. However the diastereoselectivity of this coordination was not mentioned.(9) We now report the first asymmetric addition of chiral triquinphosphorane 1c to hexacarbonylmolybdenum leading to complex 4.(10) A totally diastereoselective opening of the diazaphospholidine ring occurs and affords an enantiopure bicyclic oxazaphospholidine species, exhibiting an eight-membered ring, fused to the oxazaphospholidine ring by the P-N bond, that is coordinated to the Mo center through the p(III) phosphorus atom (Scheme 3).