Process for converting the achiral meso form or the racemate of an ansa-metallocene complex or mixtures thereof into one of its enantiomers

In a process for converting the achiral meso form or the racemate of an ansa-metallocene complex or a mixture thereof into one of its enantiomers, the conversion is carried out photochemically in the presence of an enantiomerically pure auxiliary reagent.

EXAMPLES 
The photochemical conversion was carried out by irradiation with a Phillips 
HPK 125 W mercury vapor lamp. 
Example 1 
Preparation of enantiomerically pure 
dimethylsilanediylbis(2-methyl-4-tert-butyl-1-cyclopentadienyl)zirconium 
1,1'-bi-2-naphthoxide by conversion of an rac/meso mixture. 
49 mg (0.1 mmol) of an rac/meso mixture (molar ratio 1:1) of 
dimethylsilanediylbis(2-methyl-4-tert-butyl-1-cyclopentadienyl)zirconium 
dichloride, 37 mg (0.125 mmol) of enantiomerically pure dilithium 
1,1'-bi-2-naphthoxide (prepared from R(+)-1,1'-bi-2-naphthol) and 4 ml of 
absolute toluene were placed in a Schlenk vessel under inert gas. 
Irradiation was carried out while stirring for a period of 29 hours at 
40.degree. C. The solution was subsequently decanted from the solids which 
had settled out and the solvent was taken off under reduced pressure. The 
solid residue was dissolved in 3 ml of diethyl ether and crystallized at 
-80.degree. C. to give a yellow powder. The quantitative conversion to 
enantiomerically pure 
dimethylsilanediylbis(2-methyl-4-tertbutyl-1-cyclopentadienyl)zirconium 
1,1'-bi-2-naphthoxide could be confirmed by measurement of the specific 
rotation. 
Dilithium R(+)-1,1'bi-2-naphthoxide: 
.alpha.!.sub.589 =-618.degree. (c=1, tetrahydrofuran) 
Dimethylsilanediylbis(2-methyl-4-tert-butyl-1-cyclopentadienyl)zirconium 
1,1'-bi-2-naphthoxide: 
.alpha.!.sub.589 =-780.degree. (c=1, toluene) 
.alpha.!.sub.436 =-2620.degree. (c=1, toluene) 
Example 2 
Preparation of enantiomerically pure 
dimethylsilanediylbis(2-methyl-4-phenyl-1-cyclopentadienyl)zirconium 
1,1'-bi-2-naphthoxide by conversion of the meso form 
53 mg (0.1 mmol) of 
meso-dimethylsilanediylbis(2-methyl-4-phenyl-1-cyclopentadienyl)zirconium 
dichloride, 37 mg (1.125 mmol) of dilithium 1,1'-bi-2-naphthoxide and 5 ml 
of absolute toluene were placed in a Schlenk vessel under an inert gas 
atmosphere. Irradiation was carried out while stirring over a period of 5 
hours at 40.degree. C. The solution was subsequently decanted from the 
solids which had settled out and the solvent was taken off under reduced 
pressure. The solid residue was washed with pentane and dried under 
reduced pressure. This gave 65.5 mg (=88 %) of enantiomerically pure 
dimethylsilanediylbis(2-methyl-4-phenyl-1-cyclopentadienyl)zirconium 
1,1'-bi-2-naphthoxide. 
Dilithium R(+)-1,1'-bi-2-naphthoxide: 
.alpha.!.sub.589 =-618.degree. (c=1, tetrahydrofuran) 
Dimethylsilanediylbis(2-methyl-4-phenyl-1-cyclopentadienyl)zirconium 
1,1'-bi-2-naphthoxide: 
.alpha.!.sub.589 =-750.degree. (c=0.05, toluene) 
.alpha.!.sub.436 =-2100.degree. (c=0.05, toluene)