Polymerization catalysis with transition metal amidinate and related complexes

Spontaneous vs. Base‐Induced Dehydrochlorination of Group 14 ortho‐Carboranylamidinates

“…[14] The new ligand type of ortho-carboranylamidinates was first synthesized in our laboratory in 2010 by in situ lithiation of the parent carborane, ortho-C 2 H 12 B 10 (= orthodicarba-closo-dodecaborane), followed by treatment with an equivalent amount of a carbodiimide (Scheme 1). [15] exhibits a tetrahedral coordination, were obtained in a targeted synthesis protocol by reaction of the doubly lithiated ligand Li 2 [16] Fe II and Fe III , [17] Ti IV , Zr IV , Si, and P. [18] In all cases, the ligand adopts a κC,κN-chelating mode instead of the "normal" amidinate's κN,κN′-chelating mode. Therefore, a proton is formally shifted from the carboranyl carbon atom to the amidinate unit, resulting in an amidine moiety that usually acts as a monodentate donor functionality (Scheme 2a).…”

“…[1][2][3][4] Metal complexes comprised of amidinato ligands are readily available by insertion of a carbodiimide into an M-C bond of an appropriate metal-organic precursor compound. Amidinates are typically small-bite chelating ligands, even though in some transition-metal complexes, bridgingcoordination modes, such as μ-κN:κN′, are also realized.…”

Aminopyridine stabilized group-IV metal complexes and their applications

“…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].…”

“…Their catalytic activity also increased with increasing the steric bulk of the ligand; however, their activities were lower than closely related amidinate-Ti-complexes [48][49][50][51]. The maximum catalytic activity (240 kg PE mol cat.…”

“…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.…”