341489-72-3Relevant academic research and scientific papers
Contribution to the chemistry of metal complexes with stereogenic metal centers: Diastereoselective formation of ruthenium half-sandwich complexes
Kaulen, Corinna,Pala, Corinne,Hu, Chunhua,Ganter, Christian
, p. 1614 - 1619 (2008/10/08)
The chiral half-sandwich complexes 3 and 4 are formed with high diastereoselectivities in the reaction of cyclopentadienides 2a,b, bearing tethered phosphaferrocene donor moieties with planar chirality, and [(PPh3)3RuCl2] in toluene at 90°C. The diastereoisomers of the Cp complex 3 are obtained in a 95:5 ratio, whereas for the Cp* derivative 4 only one isomer is detectable, the structure of which has been determined by X-ray diffraction. Substitution of the chloride ligand in 4 by other anionic (H-, I-) or neutral (H2, py) ligands proceeds stereospecifically in all cases. In contrast, conversion of the chlorides 3a,b (95:5) to the respective hydrides 9a,b proceeds with complete epimerization at Ru. In CHCl3 the 1:1 mixture of hydrides 9a,b is reconverted to the chlorides to give a kinetically controlled 4:1 mixture of isomers 3a,b. Equilibration of this mixture in toluene at 90°C restores the original ratio of isomers of 95:5, which we therefore believe to reflect the thermodynamically controlled value. The cationic H2 complex 7, generated via Cl abstraction from 4 in the presence of H2, was characterized to be a η2-dihydrogen complex by measuring the T1 value of the coordinated H2 ligand.
