OBSERVING A HOMOGENEOUS ZIEGLER CATALYST PRECURSOR AT WORK - INSERTION REACTIONS INTO THE ZIRCONIUM-CARBON BOND OF THE (BUTADIENE)ZRCP(2) B(C6F5)3 ADDITION PRODUCT/
B. Temme et al., OBSERVING A HOMOGENEOUS ZIEGLER CATALYST PRECURSOR AT WORK - INSERTION REACTIONS INTO THE ZIRCONIUM-CARBON BOND OF THE (BUTADIENE)ZRCP(2) B(C6F5)3 ADDITION PRODUCT/, Chemistry, 2(8), 1996, pp. 919-924
(Butadiene)zirconocene adds to B(C6F5)(3) to form the metallacyclic me
tallocene-boron betaine system 1, which contains a C-F --> Zr interact
ion. Addition of tert-butylisocyanide or tert-butylcyanide leads to cl
eavage 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 eta(2)-iminoacyl betaines 5 and 6 (
2 stereoisomers), whereas 7 inserts additional tert-butylcyanide into
the Zr-C bond to give a chiral metallacyclic N-zirconaketimine complex
that is probably stabilized by an internal berate --> 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 degree
s C in [D-8]toluene solution, are chiral and are also stabilized by in
ternal berate --> Zr coordination. Complexes 9 and 10 are likely to be
intermediates in the formation of active homogeneous Ziegler polymeri
zation catalysts.