Group 4 metal complexes bearing new tridentate (NNO) ligands: Benzyl migration and formation of unusual C–C coupled products

Aminopyridine stabilized group-IV metal complexes and their applications

“…-1 h -1 , Table 1) similar to the other reported Ti-complexes containing planar tridentate ligands [52,53]. The planar structure of the catalyst is supportive for ethylene coordination which enhances the formation of higher molecular weight polymers.…”

“…Notably, for catalyst 26, the activity as well as molecular weight of the polymer increased with increasing catalystto-MAO ratio [33]. Catalyst 26 produced higher molecular weight polymer (M w = 11,600 g mol -1 ) than similar Ti and Zr-catalysts and is attributed to its planar structure which facilitates the co-ordination of ethylene [49][50][51][52][53]. However, broader polydispersities indicated the presence of several catalytically active species in the reaction mixture, and a detailed theoretical as well as experimental investigation is required for enhancing the catalytic potential of such complexes and to control the polydispersity index [33].…”

“…The activity of Cp 2 TiCl 2 enhanced to 424 kg PE cat mol -1 h -1 when small amount of water was added due to the formation of methyl aluminoxane (MAO) by the hydrolysis of Al-alkyls . Industrial applications of metallocene-based catalysts have been tremendous; however, their limitations, for example, very high costs and inability to polymerize polar olefins, have forced the researches for alternatives, and amido ligands have been the most notable success because: (1) these ligands make two bonds with the metal resulting into a fourmembered chelate ring system and (2) they enable the incorporation of variety of functionality in remaining two substituents on N-atom and hence to dictate variety in their reactivity and selectivity (Scheme 1) [28,29,[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65]. Aminopyridinato ligands could be derived from deprotonated 2-aminopyridines, critical sub-class of amido ligands, which could provide additional advantages due to their binding modes flexibility.…”

Homopiperazine and Piperazine Complexes of ZrIV and HfIV and Their Application to the Ring‐Opening Polymerisation of Lactide

“…Zr IV dimers with bis(phenoxide) salan ligands are rare and this is the first example of a tetrameric species. [9d,17] Examples with similar ligands include those of Gibson who has observed dimers with ONN ligands, [17] we Figure 1. Solid-state structures of Zr 4 (1)(OiPr) 14 (HOiPr) 2 (top) and Zr 2 (2)(OiPr) 6 (bottom).…”

2-Aldiminophenoxytitanium chloride complexes: Synthesis, characterization, and ethylene (co-)polymerization behavior

“…Presumably, the five-coordinated complex pre-catalyst is less sterically hindered, and consequently the co-monomer was more readily taken up [47]. The pre-catalyst II exhibited appreciable activity in both ethylene polymerization and co-polymerization [48], whereas the pre-catalysts III that possessed a 1-methyl-2-benzimidazolylmethyl group, produced an activity of 150 kg polymer/(mol (Ti) h bar) for ethylene polymerization only in the presence of i Bu 3 Al/DMAO, but produced polyethylenes with large PDI values (w48) [49]. The tridentate titanium complex precatalyst IV exhibited a low activity for ethylene polymerization, and with a broad distribution of polyethylene molecular weights [50].…”