Titanium compounds, spectra

Ti(III) is considered to be the active species in the SPS polymerization. The H-NMR spectrum of the reacted materials between the titanium compounds and MAO does not show the titanium compound peaks. This also supports the trivalent titanium as the active site. Newman and Malanga [18] synthesized... 

The reaction between 1 equiv. of the sterically bulky COT" (GOT" = l,4-bis(trimethylsilyl)cyclooctatetraene) ligand and TiCl3(THF)3 did not result in the clean formation of an analogous compound to 160.119 Instead, a mixture of the Ti(n) species (COT")2Ti, the mixed valence Ti(m)/Ti(iv) species (COT")Ti 2(/x-Gl)3 166 and the asymmetric Ti(m) dimeric species (GOT")Ti(/x-Gl) 2(THF) 167 were formed in yields of 15%, 30% and 50%, respectively. X-ray crystallography confirmed that only one of the Ti centers in 167 coordinates to a molecule of THF, although this THF was released when 167 was warmed to 80 °G in vacuo. The EPR spectrum of 167 confirmed that the two Ti centers contained unpaired electrons while that of 166 was consistent with a GOT" Ti(m) species. No unusual line broadening was observed in the EPR spectra of 166 when it was cooled this suggested that the EPR relaxation time was relatively fast compared to any electron transfer between the two titanium centers. 

Titanium derivatives containing carbazole (cb) ligands have been isolated and studied. Reaction of Ti(CH2SiMe3)4 with carbazole yields the alkylidene-bridged dimer [Ti(/i-CHSiMe3)(cb)2]2 (Scheme 106). A singlet at 8 14.75 is observed in the 1H NMR spectrum of the alkylidene complex. The reaction of this compound with 2,6-dimethyl-phenyl isocyanide leads to titanium derivatives containing new carbon-carbon bonds (Section 4.05.2.3).109,110... 

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