New catalysts for olefin polymerization: from elementary processes to the synthesis of polyolefins

Ethylene polymerization with methylaluminoxane/(nBuCp)2ZrCl2 catalyst supported on silica and silica‐alumina at different AlMAO/Zr molar ratios

“…In general, the broad band placed around 350 nm suggests the presence of monomethylated species like [(nBuCp) 2 ZrCH 3 ] þ [MAOCl] À . 28,[30][31][32] In addition, the UV-Vis spectra of silica-alumina-supported catalysts show an absorption band at higher wavelengths ($ 450 nm) related with the presence of more cationic active species with further ionic pair dissociation. This band only appears in silica-alumina and is more intense at lower Zr loading because at higher Zr percentages, it increases the probability to get zirconocene dimers (i.e., electron deficient bridging complexes of two Zr centers), which compete for Zr atoms reducing the formation of [(nBuCp) 2 ZrCH 3 ] þ [MAOCl] À active species.…”

Ethylene Oligomerizations by Sterically Modulated Salicylaldimine Cobalt(II) Complexes Combined with Various Alkyl Aluminum Cocatalysts

“…These attempts on several zirconocene/MAO systems [26][27][28][29][30] and a-diimine-[N,N]NiBr 2 /MAO system [31] for olefin polymerizations have contributed much to understand the successive elementary steps involved in the formation of cationic active…”

“…There had been a considerable number of theoretic and experimental investigations on early and late transition metal complexes to elucidate their active species formed during olefin polymerizations [25][26][27][28][29][30][31]. These attempts on several zirconocene/MAO systems [26][27][28][29][30] and a-diimine-[N,N]NiBr 2 /MAO system [31] for olefin polymerizations have contributed much to understand the successive elementary steps involved in the formation of cationic active…”

Highly active and stereospecific polymerizations of 1,3-butadiene by using bis(benzimidazolyl)amine ligands derived Co(II) complexes in combination with ethylaluminum sesquichloride

“…Processes involving the active species generation have been successfully evaluated by UV-vis spectroscopy for metallocene catalyst system by Cramail and coworkers [36][37][38][39]. They further extended their study to Ni-diimine catalysts [40].…”