Catalyst for Highly Enantioseleetive Hydrogenations

The molecular structure and absolute configuration of the title compound, [Rh(trinorbornadiene) { (+)-binap }](CIO4), have been determined by the single-crystal X-ray diffraction method. The crystal data are: [Rh(CTHs)(C44HaEP2)]C104, orthorhombic, P2~2~21, Z = 4, a = 11.104 (1), b = 35.238 (2), c = 10.892 (1) A, U = 4261.6 (3) A 3, D x = 1.430 Mg m -a,/a(Cu Ka) = 4.98 mm -~. The structure has been refined, using 3249 independent reflections, to give an R value of 0.032. The Rh I has square-planar coordination geometry involving two P atoms and the two C=C bonds of norbornadiene. The seven-membered chelate ring is fixed in a 2 skew(v) conformation and this dissymmetry determines the orientation of the four phenyl rings on the P atoms. A chiral environment at the site of the olefin coordination is provided by the dispositions of the four phenyl rings in an alternating edge-face manner. The absolute configuration of the dextrorotatory diphosphine ligand has been assigned by the Bijvoet method as R.