Enhanced production of bridged hafnocenes
US5760262A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 17, 1997 |
| Grant date | Jun 2, 1998 |
| Priority date | — |
| Expiry date | Jun 17, 2017 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07F17/00
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
The reaction between a hafnium tetrahalide-diamine adduct and a metallated bis(cyclopentadienyl-moiety containing) ligand, offers great promise as a way of producing racemic hafnocenes, but involves a number of complications. Tetrahydrofuran, a commonly-used solvent/diluent for such reactions, when present in substantial portions in the liquid reaction medium containing the reactants and/or reaction product(s) has been found to cause a substantial reduction in yields of chiral hafnocenes. Apparently the presence of a substantial amount of THF causes or at least results in the formation of increased amounts of the undesirable meso isomer, tends to cause or result in tar formation, and results in a product having poor filterability. Thus large amounts of THF if fed to the reactor with the reactant(s) are purged to a suitably low level, replaced by a liquid aromatic hydrocarbon, and then the reaction mixture is heated to a higher reaction temperature. Large amounts of liquid paraffins and free diamine in the reaction mixture during reaction also contribute to tar formation and reduction in yields of chiral hafnocene. Thus the presence of such materials in the reaction mixture is kept …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.