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A new synthetic route to arylchalcogenyl‐sulfonate ligands (E,SO) (E = Se, S) and the synthesis and ethylene reactivity of two new nickel complexes [NiCl(py)(E,SO)] (Ni1, E = Se; Ni2, E = S) are reported. The minimum energy structures of the complexes were determined by density functional theory (DFT) calculations. For both compounds, the triplet and singlet 1 structures (with Cl trans to chalcogen) are higher in energy compared with singlet 2 (with Cl cis to chalcogen). Under initial catalytic condition (MAO, [Al/Ni] = 300, time = 20 min, T = 30°C) complex Ni1 oligomerizes ethylene with turnover frequencies (TOF) of 32.6 × 103 (mol ethylene) (mol Ni)−1 (h)−1 with 81.3% of 1‐butene production. The use of different cocatalyst systems (MAO/TMA or MAO/TiBA in an equimolar ratio) led to lower activities and poor selectivity for 1‐C4. Under optimized reaction conditions (MAO, [Al/Ni] = 600, time = 20 min, T = 30°C), the phenylthionyl complex Ni2 was 1.7 times more active than the phenylselenyl analog, with TOF of 72.3 × 103 (mol ethylene) (mol Ni)−1 (h)−1 with 84.3% of 1‐butene selectivity. DFT calculations suggest that the lowest lowest unoccupied molecular orbital (LUMO) energy and highest natural charge at the Ni center could be associated to the higher activity of Ni2 compared with the phenylselenyl analog Ni1. [ABSTRACT FROM AUTHOR]

In this work, a new family of chromium complexes supported by bis(pyrazolyl)thioether/amine ligands containing pendant O‐ and N‐donor groups CrCl3{S‐bis[(3,5‐DMPz)methyl]sulfide} (2a), CrCl3{N‐bis[(3,5‐DMPz)benzylamine]} (2b), CrCl3{N‐bis[(3,5‐DMPz)butylamine]} (2c), [CrCl2{N‐bis[(3,5‐DMPz)methyl][(2‐pyridinyl)methyl]amine}]Cl (2d), [CrCl2{N‐bis[(3,5‐DMPz)methyl][quinoline]amine}]Cl (2e), [CrCl2{N‐bis[3,5‐DMPz‐methyl][EtNMe2]amine}]Cl (2f), CrCl3{N‐bis[(3,5‐DMPz)methyl][2‐methoxyphenyl]amine} (2g), and CrCl3{N‐bis[2‐(3,5‐DMPz)methyl][(2‐pyridyl)ethyl]amine} (2h) were synthetized and characterized by elemental analysis and Fourier transform infrared spectroscopy (FTIR) spectroscopy. Density functional theory (DFT) calculations demonstrated that the pendant group as well as the spacer between the N‐donor group and the central amine nitrogen have strong influence on the coordination motif of the ligand. Thus, 1d–1f act as tetradentate ligands while 1g and 1h preferably coordinated to the chromium metal center in a tridentate [N,N,N] mode fashion. The catalytic performance of 2a–2h is strongly influenced by the nature of the central bridging atom (S, N) as well as the pendant O‐ and N‐donor group. Upon activation with methylaluminoxane (MAO), chromium precatalysts 2a–2c, 2e, and 2f generated active systems producing oligomers ranging from C4 to C12+ with a high selectivity for α‐olefins (>82.4%). On the other hand, precatalysts bearing pyridine (2d and 2h) and methoxy (2g) functionalized amine bis (pyrazolyl) ligands exclusively produce polyethylene (PE) with activities in the range of 107.2–372.0 kg of PE·mol[Cr]−1 h−1. [ABSTRACT FROM AUTHOR]