| The planar-chiral arene-tethered complex Ru(eta6:eta 1-Me2NC6H4C6H4 PCy2) Cl2 has been converted into a variety of neutral, cationic, and dicationic derivatives. Specifically, complexes with phosphine, bisphosphine monosulfide, diamine, N-heterocyclic carbene, carbonyl, alkyl, allenylidene, olefin, and hydride ligands have been prepared and studied. Many of these derivatives are chiral-at-metal, and a strong controlling influence of the planar-chiral arene-tethered ligand on the metal chirality was noted. The synthetic routes to the various new complexes are detailed, and are accompanied in most cases by an analysis of the stereodynamics.; Three catalytic applications were found and investigated: asymmetric Diels-Alder reactions, asymmetric hydrogenations of ketones, and cyclizations of 1,6-enynes. For the first of these, the Diels-Alder reaction of methacrolein and cyclopentadiene, the ligand architecture was varied in an attempt to optimize the selectivity of the catalyst for this reaction. The best case resulted from the complex with the chiral phosphoramidite (S)-MonoPhos, for which an enantiomeric excess (ee) of 70% was obtained. The hydrogenation of prochiral ketones (e.g. acetophenone) was catalyzed by complexes with the chiral diamine (S, S)-DPEN as a ligand. This reaction proceeds smoothly under 8 atm of hydrogen pressure, in iPrOH, and with NaOtBu as an activator; ee's of up to 61% were observed. The cyclization (cycloisomerization and hydroxycyclization) of 1,6-enynes is catalyzed by the species generated in situ from the addition of AgSbF6 to Ru(eta6:eta1-Me 2NC6H4C6H4PCy2 ) Cl2. The observed products were the result of skeletal rearrangements, and labeling studies suggested a mechanism involving alkyne activation by the acidic metal catalyst.; Rh complexes of the form Rh(cod)(NHC*)Cl and [Rh(cod)(NHC*) (L)]SbF6, where NHC* is a chiral monodentate N-heterocyclic carbene, and L is an N-heteroarene, were prepared by silver transmetalation. The stereodynamics were probed, and it was found that the complexes undergo fast rearrangements, although very high conformational preferences exist. Both the neutral and cationic complexes were applied as catalysts for the asymmetric hydrosilylation of acetophenone, with ee's up to 58%.; W complexes of the form W(CO)2(eta3-crotyl) (diphos)X, where X is a halide, have been prepared and studied previously in our laboratory. In this study, low temperature NMR spectroscopy was used to evaluate the diastereomeric preferences elicited by the unsymmetrical crotyl ligand. Also, an influence of the halide ligand on the anti/syn geometry of the crotyl ligand was observed; a preference for the anti isomer correlated with larger halide ligands. Finally, the dynamics and reactivity of a cationic, tricarbonyl analogue [W(CO)3(eta 3-crotyl)(diphos)]SbF6 was explored. This complex was found to be more reactive and much less prone to racemization than its neutral precursors. |
