OCTAHEDRAL COMPLEXES WITH PREDETERMINED HELICAL CHIRALITY - XYLENE-BRIDGED BIS([4,5]-PINENO-2,2'-BIPYRIDINE) LIGANDS (CHIRAGEN[O-XYL, M-XYL, P-XYL]) WITH RUTHENIUM(II)

Tetradentate ligands are obtained by joining two optically active [4,5 ]-pineno-2,2'-bipyridine molecules in a stereoselective reaction, wher e two new stereogenic centers are created. These ligands are new membe rs of the chiragen family that form OC-6 complexes with predetermined helical chirality. Ru(II) complexes with 4,4'-dimethyl-2,2'-bipyridine occupying the remaining coordination sites have been synthesized with all three new ligands. Characterization of the ruthenium complexes by NMR spectroscopy confirm C-2-symmetric structures in solution. CD spe ctra show that the complexes are composed of only one helical diastere omer with the expected absolute configurations. In addition, a strong chiral amplification is observed, if precursors of low enantiomeric pu rity are used. This is due to the inability of ligands that are hetero chiral in the two bpy moieties to coordinate to one center. X-ray stru ctural data were obtained for the complex Delta-[RuCG[o-xyl](4,4'-DMbp y)](PF6)(2). Crystal data (Mo K alpha, 298 K): trigonal, space group R 3, a = 52.986(4) Angstrom, c = 10.545(1) Angstrom, V = 25639(4) Angstr om(3), Z = 18, R1 = 0.087, and wR2 = 0.0986 for 2609 observed reflecti ons.