Synthesis, crystal structure and reaction of differentially ring-substituted titanocene dichlorides
SummaryA new class of differentially ring-substituted titanocene dichlorides of the type Cp′Cp″TiCl2 has been prepared by reacting Cp″M (M=Li, K; Cp″=RC5H4) with Cp′TiCl3 (Cp′=MeOCH2CH2C5H4). The crystal structure of Cp′(PhCEt2C5H4)TiCl2, the first example, has been determined by x-ray diffraction and refined to a final R factor of 0.0532 for 2304 reflections. The crystal belongs to the monoclinic space group C2h5−P21/c with unit cell parameters:a 10.205(6),b 13.003(5),c 17.591(9) Å, β 101.91(4)°, V=2284 Å3, Z=4 and Dc=1.32 g/cm−3. Replacement of one neomenthyl in bis(neomenthyl-cyclopentadienyl)titanium dichloride by one MeOCH2CH2 — raises the e.e. value from 5.8% to 11.2% in the catalytic asymmetric hydrogenation of 2-phenyl-1-butene.
Chiral cyclopentadienyl as ligands in homogeneous asymmetric catalysis Part 1. Asymmetric hydrogenation of simple olefins by Ti(IV) complexes
Abstract The stereodifferentiating activity of Ziegler—Natta type Ti(IV) catalysts carrying the chiral ligands menthyl or neomenthyl cyclopentadienyl has been investigated in the asymmetric homogeneous catalytic reduction of a prochiral olefin such as 2-phenyl-1-butene, which is hydrogenated with acceptable optical yields to (R)-(−) or (S)-(+)-2-phenyl-1-butane, respectively The effect on the optical yields of the reaction temperature, of the nature of the chiral cocatalyst or of achiral cocatalysts of different bulk has also been studied.
Self-assembly of pyridinium-tailored anthracene amphiphiles into supramolecular hydrogels.
The mixing of a polyacid cross-linker with a pyridinium-functionalized anthracene amphiphile afforded a supramolecular hydrogel through a self-assembly process that was primarily driven by π-stacking and electrostatic interactions.