Chiral induction in transition metal compounds and catalysts.

摘要

Molybdenum and tungsten complexes of the formula M(CO)2(eta 3-C4H7)(L-L)X (M = Mo or W, C4H 7 = syn-crotyl, L-L = diphos or (S,S)-chiraphos) resolve spontaneously via a crystallization induced asymmetric transformation (CIAT). In the diphos complexes the conglomerate that forms allows for manual separation of the chiral-at-metal enantiomers since the size of the crystals are often adequately large. In the (S,S)-chiraphos complexes the equilibration of the two diastereomeric forms in solution leads to a single isomer upon crystallization. Kinetic measurements by CD spectroscopy yielded the half lives and barriers of isomerization for those complexes, showing that epimerizations of this kind can be controlled at ambient temperature.; A series of molybdenum allyl complexes bearing the Klaui ligand LOMe have been synthesized and characterized by X-ray crystallography. All complexes show an exo conformation of the allyl. The dynamic behavior of LOMeMo(CO)2(eta3-C 3H5) and syn-LOMeMo(CO) 2(eta3-crotyl) has been elucidated by VT 1H NMR. The chiral non-racemic Klaui ligand L(S)-BINOL has also been synthesized. It contains a tridentate anionic ligand that has C 3 symmetry.; The use of the phosphines P(Cy)x(Ph)3-x (x = 1--3) as ligands in the palladium catalyzed alkylation of 3-but-1-enyl ethyl carbonate allylic substrates led to regio- and stereochemical memory effects. Bulky N-heterocyclic carbenes also gave memory effects when used as ligands for palladium. Elucidation of the intramolecular racemization mechanism of the eta3-crotyl in (eta3-crotyl)Pd(NHC- tBu)Cl was accomplished by spin saturation transfer (SST) and 1H VT NMR. The barrier for this racemization was found to be 18.3 Kcal/mole.; The ruthenium complexes (eta6-cymene)Ru(mu-Cl) 3Ru(BIPHEP)Cl, (eta6-cymene)Ru(mu-Cl)3Ru(BIPHEP)(MeCN)SbF 6 and (eta6-cymene)Ru(mu-Cl)3Ru(BIPHEP)(CO)SbF 6 have been synthesized and characterized by X-ray crystallography. Substitution of the eta6-cymene ring for the isoelectronic set of ligands [(P-P),Cl-] provides the possibility for asymmetric induction between the two different Ru centers.; The solid state structure and solution dynamics of the complexes (eta 3-allyl)Pd(Lx)SbF6 (L1 = 2-diphenylphosphino-2'-(N,N-dimethylamino)biphenyl, L2 = 2-dicyclohexylphosphino-2'-( N,N-dimethylamino)biphenyl) have been elucidated by X-ray crystallography, CD spectroscopy and NMR experiments such as COSY, EXSY and HMQC. Ligand L 2 shows a novel coordination mode where the NMe2 group is not bound to palladium. Instead, L2 is bound to palladium through the phosphorus and a C-C double bond from the ring bearing the NMe 2 group.