New neutral nickel(II) complexes bearing asymmetric β-ketoiminato (N,O) ligands (5ac), [(2,6-i Pr 2 C 6 H 3 )NC(R 2 )C(H)C(R 1 )O]Ni(Ph)(PPh 3 ), have been synthesized. X-ray crystal structures reveal that each of complexes 5a-c adopts a near square-planar coordination geometry and the triphenylphosphine group is always trans to the arylamine group. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 5a-c can promote the polymerization of methyl methacrylate (MMA) in excellent yields (>98%), producing syndiotactic-rich PMMAs (rr around 70%). It is very exciting that the 5a-c/MMAO catalyst systems exhibit highly catalytic activities for the copolymerization of ethylene with MMA, producing high molecular weight functionalized polyethylenes with up to 16.7 mol % of methacrylate units built into the moderately branched polyethylene backbone. Further mechanistic studies have shown that PMMAs and copolymers obtained using these complexes possibly arise from a coordination-insertion mechanism rather than a radical mechanism.

A novel organocatalytic olefinic carbon-sulfur bond forming reaction was developed. Under the catalysis of 10 mol% stable N-heterocyclic carbene, thiols undergo direct nucleophilic substitution reaction with gem-difluoroalkenes to produce α-fluorovinyl thioethers in high yields with excellent Z-selectivity. In this process, bases are not necessary.

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846–031 during its outburst in 2019 with the observations of Insight-HXMT, NICER and MAXI. This outburst can be classified roughly into four different states. Type-C quasi-periodic oscillations (QPOs) observed by NICER (about 0.1–6 Hz) and Insight-HXMT (about 0.7–8 Hz) are also reported in this work. Meanwhile, we study various physical quantities related to QPO frequency. The QPO rms–frequency relationship in the energy band 1–10 keV indicates that there is a turning pointing in frequency around 2 Hz, which is similar to that of GRS 1915+105. A possible hypothesis for the relationship above may be related to the inclination of the source, which may require a high inclination to explain it. The relationships between QPO frequency and QPO rms, hardness, total fractional rms and count rate have also been found in other transient sources, which can indicate that the origin of type–C QPOs is non-thermal.