Zirconium Complexes of a Rigid, Dianionic Pincer Ligand: Alkyl Cations, Arene Coordination, and Ethylene Polymerization

Abstract

Reaction of 4,5-bis(2,4,6-triisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene (H 2 XN 2 ) with [Zr-(NMe 2 ) 4 ], followed by crystallization from O(SiMe 3 ) 2 , yielded [(XN 2 )Zr(NMe 2 ) 2 ]•{O(SiMe 3 ) 2 } 0.5 (1•{O(SiMe 3 ) 2 } 0.5 ). The zirconium dimethyl complex [(XN 2 )ZrMe 2 ] (2) was subsequently accessed (a) by treatment of 1•(O(SiMe 3 ) 2 ) 0.5 with excess AlMe 3 or (b) via reaction of 1•(O(SiMe 3 ) 2 ) 0.5 with excess Me 3 SiCl, affording [(XN 2 )ZrCl 2 ] (3) followed by reaction of 3 with 2 equiv of MeLi. Reaction of [(XN 2 )ZrMe 2 ] (2) with one equiv of B(C 6 F 5 ) 3 or [CPh 3 ][B(C 6 F 5 ) 4 ] yielded cationic [(XN 2 )ZrMe][MeB(C 6 F 5 ) 3 ] (4) and [(XN 2 )ZrMe(arene)][B(C 6 F 5 ) 4 ] {arene = η 6 -benzene (5a), η 6 -toluene (5b), or bromobenzene (5c)}, respectively. Both 4 and 5b are active for ethylene polymerization under 1 atm of ethylene at 24 and 80 °C in toluene with activities ranging from 23.5−883 kg mol −1 atm −1 h −1 , yielding polymers with weight-average molecular weights (M w ) of 70,800−88,100 g mol −1 and polydispersities (M w /M n ) of 3.94−4.67.

Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure

“…On the way of synthesizing polyolefin with unique characterizations with narrow molar mass distributions and branching degree, academic and industrial researchers have devoted their consideration in polymer science and organometallic chemistry [ 1 , 2 , 3 , 4 ]. To design new polymerization technologies based on transition metal compound, homogeneous metallocene single-site catalyst precursors and main-group organometallic alkylaluminum cocatalysts can be considered valuable strategies to achieve this goal [ 5 , 6 , 7 , 8 , 9 ]. Homogeneous metallocene catalyzed polyolefin has become an interesting topic over the past decade and the commercialization of homogeneous metallocene catalyst is expected to be a revolution in the polymer industry [ 10 , 11 , 12 , 13 ].…”

NON‐Ligated N‐Heterocyclic Tetrylenes

“…Additional stirring overnight, evaporation of all volatiles and 1 H NMR spectroscopic monitoring revealed, however, that the remaining powders solely contain [Me 3 NÀ W(CO) 5 ] (δ 1H (NMe 3 ) = 2.00 ppm) and the hydrolysis products of 3-5 (δ 1H (NH) = 5.95 ppm). Furthermore, two signals in the 13 C NMR spectra at 5), C55À O3 = 1.126( 5), O4À C56 = 1.144(4), O5À C57 = 1.140(4), N1À Sn1À N2 = 118.87(9), Rh1À Cl2 = 2.3835( 10), Rh2À Cl1 = 2.3727(8), Rh2À Cl2 = 2.3725( 9), Rh1À C54 = 1.812(4), Rh1À C55 = 1.922(4), Rh2À C57 = 1.836(4), Rh2À C56 = 1.824(4 δ 13C = 199.6 and 201.3 ppm belonging to the CO carbon atoms, further underline the formation of [Me 3 NÀ W(CO) 5 ] (for details see ESI, Section S1). We believe the inhibited reactivity of the NHTs can at least partly be attributed to steric and kinetic effects.…”

“…[12] The NON ligand (NON = 4,5-bis(2,6-diisopropylphenylamino)-2,7-di-tert-butyl-9,9-dimethylxanthene) has been employed in some actinide, yttrium, and zirconium complexes. [13] In main group chemistry, however, fewer examples are known. For instance, Aldridge and Goicoechea have described recently a highly reactive nucleophilic Al(I) compound stabilized by the NON-backbone (D in Scheme 1).…”

Tetrakis(dicyclohexylamido)zirconium(IV)

“…Amido complexes of group 4 metals play an important role in synthetic chemistry. They are widely used as catalysts in hydroaminoalkylation reactions (Roesky et al, 2009) or in the catalysis of olefin polymerization reactions (Shafir & Arnold, 2001;Motolko et al, 2017). Tetrakis(dialkylamido)zirconium(IV) compounds are commonly known as precursors of a variety of more complex zirconium-containing compounds (Diamond et al, 1995(Diamond et al, , 1996.…”