IR and NMR studies on zirconocene dichloride/methylalumoxane systemscatalysts for olefin polymerization

Methylalumoxane – History, Production, Properties, and Applications

“…Unfortunately, acquiring reliable 27 Al NMR spectroscopic data is not straightforward, because of the high quadrupole moment of the Al nucleus, which results in broad, poorly defined signals, making interpretation difficult and highly contradicting. Broad resonances at 149–153 ppm (fwhm 1750 Hz) have been found that coincide with the signal for Me 3 Al at δ = 153 ppm (fwhm 850 Hz) 58,59. Other studies, however, claim that the 27 Al signal of MAO is too broad to be visible under standard conditions.…”

Catalytic dehydrogenation of cyclooctane with titanium, zirconium and hafnium metallocene complexes

“…MAO consists of a variety of linear and cyclic oligomers which exist in a dynamic equilibrium [33][34][35][36][37][38][39].…”

Investigation and Study of Monomers and Polymers Based on Known Metal Induced Couplings of Alkynes and Diynes

“…There was no unreacted zirconocene dichloride observed supported by the lack of a singlet resonance signal at δ = 5.90 ppm. 93 Negishi et al (method 2) described the mechanism by which zirconocene dichloride becomes reactive. 91 Negishi et al demonstrated via in situ 1 H NMR spectroscopy study that with the addition of n-BuLi to a solution of zirconocene dichloride in THF that n-BuLi reduces zirconocene into a highly reactive species (i.e.…”

“…However, the resonance signal at δ = 5.87 ppm is consistent with the formation of zirconocene dichloride during the reaction. 93 The formation of zirconocene dichloride suggests that metallacycle transfer with CrCl 3 (THF) 3 may have occurred, as there was no other source of chlorides available. The singlet resonance signal at δ = 7.16 ppm is characteristic of benzene.…”