Source: Dissertation Abstracts International, Volume: 68-12, Section: B, page: 8022.

Adviser: J. W. Faller.

The relatively inexpensive chiral monodentate phosphoramidite ( S)-MONOPHOS was used in combination with pyridines to prepare iridium complexes which are effective for catalysis of asymmetric imine hydrogenation with comparable enantioselectivity to some of those containing more costly chiral bidentate phosphines. [Ir(cod)((S)-MONOPHOS)(L)][BArF] (cod = 1,5-cyclooctadiene; L = 3-methylisoquinoline, acridine, 2,6-lutidine, acetonitrile, or 2,3,3-trimethylindolenine; BArF = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) are efficient catalysts for the asymmetric hydrogenation of 2,3,3-trimethyfindolenine. An important observation is that the catalyst containing acridine is more enantioselective than the catalyst derived from 2,3,3-trimethylindolenine, which suggests that the other N-donor ligands are not readily displaced by the substrate during the catalytic cycle.

The axially chiral complexes [Rh(diene)(1-alkyl-3-methylimidazol-2-ylidene)(( S)-MONOPHOS)]+ (diene = 1,5-cyclooctadiene, 2,5-norbornadiene) were prepared diastereoselectively with the same chiral phosphoramidite combined with unsymmetrically substituted N-heterocyclic carbenes. Variation of the diene and the bulky N-substituent allowed tuning of the rate of ligand rotation, and diastereomerically pure complexes were obtained via crystallization.

Complexes with heterobidentate chiral and achiral P,P=S donor ligands were synthesized. Complexes [Pd(eta3-C 3H5)(Ph2P-Q-P(S)Ph2)][SbF6] impart high regioselectivity on palladium catalyzed allylic alkylations. The bite angles, the ligand hemilability, and the fluxional processes of the allylic ligands of these complexes were examined. [Re(CO)3(P,P=S )Br] (P,P=S = (S)-BINAP(S), ( S)-3,5-xylyl-BINAP(S), (2S,4S)-BDPP(S)) were shown to induce some enantioselectivity in rhenium-catalyzed allylation of aldehydes. Both the chiral and the achiral P,P=S donor ligands offer advantages over their P,P analogues for catalytic reactions in terms of catalytic activity, regioselectivity or enantioselectivity.