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Observing a Homogeneous Ziegler Catalyst Precursor at Work: Insertion Reactions into the Zirconium – Carbon Bond of the (Butadiene)ZrCp 2 /B(C 6 F 5 ) 3 Addition Product
Author(s) -
Temme Bodo,
Karl Jörn,
Erker Gerhard
Publication year - 1996
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19960020805
Subject(s) - zirconium , catalysis , chemistry , metallocene , cyanide , boron , polymer chemistry , homogeneous catalysis , medicinal chemistry , polymerization , crystallography , organic chemistry , polymer
(Butadiene)zirconocene adds to B(C 6 F 5 ) 3 to form the metallacyclic metallocene–boron betaine system 1 , which contains a C–F → Zr interaction. Addition of tert ‐butylisocyanide or tert ‐butyl‐cyanide leads to cleavage of the zirconium – fluorine linkage and formation of the adducts 4 and 7 , respectively. With additional tert ‐butylisocyanide, 4 reacts further to yield the corresponding η 2 ‐imino‐acyl betaines 5 and 6 (2 stereoisomers), whereas 7 inserts additional tert ‐butyl‐cyanide into the Zr–C bond to give a chiral metallacyclic N‐zirconaketimine complex that is probably stabilized by an internal borate → Zr interaction. Ethene and propene insertion reactions into the Zr ‐ C bond of 1 follow a similar course: the mono‐insertion products 9 and 10 , respectively, generated in situ and characterized by NMR spectroscopy at – 35°C in [D 8 ]toluene solution, are chiral and are also stabilized by internal borate → Zr coordination. Complexes 9 and 10 are likely to be intermediates in the formation of active homogeneous Ziegler polymerization catalysts.