English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Ethylene tetramerization catalyst systems comprising a Cr(III) complex containing PNP ligands and methylaluminoxane (MAO) are useful for the production of 1-octene. However, a concern with these systems is the use of expensive MAO in excess. Herein, we report a catalytic system that avoids the use of MAO. Metathesis of CrCl 3 (THF) 3 and [(CH 3 CN) 4 Ag] + [B(C 6 F 5 ) 4 ] - afforded [L 4 Cr III Cl 2 ] + [B(C 6 F 5 ) 4 ] - (L = CH 3 CN or tetrahydrofuran (THF)), which was converted to [(PNP)CrCl 2 L 2 ] + [B(C 6 F 5 ) 4 ] - , where PNP is iPrN(PPh 2 ) 2 ( 1 ) or [CH 3 (CH 2 ) 16 ] 2 CHN(PPh 2 ) 2 ( 2 ). The molecular structures of [(THF) 4 Cr III Cl 2 ] + [B(C 6 F 5 ) 4 ] - and [ 1 -CrCl 2 (THF) 2 ] + [B(C 6 F 5 ) 4 ] - were unambiguously determined by X-ray crystallography. The cationic (PNP)Cr III complexes paired with [B(C 6 F 5 ) 4 ] - anions, that is, [(PNP)CrCl 2 (CH 3 CN) 2 ] + [B(C 6 F 5 ) 4 ] - , exhibited high activity in chlorobenzene when activated with common trialkylaluminum species (Me 3 Al, Et 3 Al, and iBu 3 Al). The activities and selectivity were comparable to those of the original MAO-based Sasol system ( 1 -CrCl 3 /MAO). When activated with Et 3 Al or iBu 3 Al, the Cr complex, [ 2 -CrCl 2 (CH 3 CN) 2 ] + [B(C 6 F 5 ) 4 ] - , which bears long alkyl chains, showed high activity in the more desirable methylcyclohexane solvent (89 kg/g-Cr/h) and much higher activity in cyclohexene (168 kg/g-Cr/h). Other advantages of the [ 2 -CrCl 2 (CH 3 CN) 2 ] + [B(C 6 F 5 ) 4 ] - /Et 3 Al system in cyclohexene were negligible catalyst deactivation, formation of only a negligible amount of polyethylene side product (0.3%), and formation of fewer unwanted side products above C10. The [B(C 6 F 5 ) 4 ] - anion is compatible with trialkylaluminum species once it is not paired with a trityl cation. Hence, [(PNP)CrCl 2 (CH 3 CN) 2 ] + [B(C 6 F 5 ) 4 ] - /Et 3 Al exhibited a significantly higher activity than that of a previously reported system composed of [Ph 3 C] + [B(C 6 F 5 ) 4 ] - , that is, 1 /CrCl 3 (THF) 3 /[Ph 3 C] + [B(C 6 F 5 ) 4 ] - /Et 3 Al.

Methylaluminoxane-Free Chromium Catalytic System for Ethylene Tetramerization