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A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers.

HMBG1 is a protein expressed in natural killer cells and is important in immunosurveillance. In this study, the authors show that HMGB1 binds to and inhibits PKM2, resulting in a block in aerobic glycolysis and ultimately cell death.

Condensation of phthalodinitrile and 2-amino-5,6,7,8-tetrahydroquinoline gave the bis(2-pyridylimino)isoindole protioligand 1(thqbpiH) in high yield. Deprotonation of thqbpiH (1) using LDA in THF at −78 °C yields the corresponding lithium complex [Li(THF)(thqbpi)] (2) in which the lithium atom enforces almost planar arrangement of the tridentate ligand, with an additional molecule of THF coordinated to Li. Reaction of cobalt(ii) chloride or iron(ii) chloride with one equivalent of the lithium complex 2in THF led to formation of the metal complexes [CoCl(THF)(thqbpi)] (3a) and [FeCl(THF)(thqbpi)] (3b). The paramagnetic susceptibility of 3a,bin solution was measured by the Evans method (3a: μeff= 4.17 μB; 3b: μeff= 5.57 μB). Stirring a solution of 1and cobalt(ii) acetate tetrahydrate in methanol yielded the cobalt(ii) complex 4which was also accessible by treatment of 3awith one equivalent of silver or thallium acetate in DMSO. Whereas 3a,bwere found to be mononuclear in the solid state, the acetate complex 4was found to be dinuclear, the two metal centres being linked by an almost symmetrically bridging acetate. For all transition metal complexes paramagnetic 1H as well as 13C NMR spectra were recorded at variable temperatures. The complete assignment of the paramagnetic NMR spectra was achieved by computation of the spin densities within the complexes using DFT. The proton NMR spectra of 3aand 3bdisplayed dynamic behaviour. This was attributed to the exchange of coordinating solvent molecules by an associative mechanism which was analysed using lineshape analysis (ΔS≠= −154 ± 25 J mol−1K−1for 3aand ΔS≠= −168 ± 15 J mol−1K−1for 3b). [ABSTRACT FROM AUTHOR]

Quinolyl-substituted half-sandwich complexes (CpQ)Ln(AlMe4)2(CpQ= 2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl; Ln = Y, La) were obtained in quantitative yield via protonolysis reactions utilizing HCpQand homoleptic tetramethylaluminates Ln(AlMe4)3. X-ray structure analyses revealed that the quinolyl-substituted cyclopentadienyl ligand coordinates to the rare-earth metal centers in an η5:η1fashion through the Cp ring carbon atoms and the N atom of the quinolyl substituent. The complexes (CpQ)Ln(AlMe4)2show good activity and high trans-1,4-stereoselectivity (maximum 93%) in the polymerization of isoprene upon activation with the organoborates [Ph3C][B(C6F5)4] and [PhNMe2H][B(C6F5)4]. The effects of metal size, cocatalyst, temperature, and solvent were assessed in these polymerization reactions, and the performance of such N-donor-functionalized complexes was compared to that of (CpR)Ln(AlMe4)2containing different types of nondonor-functionalized cyclopentadienyl ligands. [ABSTRACT FROM AUTHOR]

The addition of aluminium alkyls to terminal olefins leads to branched organoaluminium compounds which can be converted into functionalised alkanes. This carboalumination reaction is efficiently catalysed by a donor functionalised Cp-chromium(III) complex. The active catalyst is obtained by activation of the chromium(III) dichloride precursor with MAO or with a mixture of trialkylaluminium and N,N-dimethylanilinium tetrakispentaflourphenylborate. Primary aminoalkenes deactivate the catalyst whereas secondary and tertiary aminoalkenes can also be carboaluminated. [ABSTRACT FROM AUTHOR]