Nickel-based ethylene oligomerization catalysts supported by PNSiP ligands

Catalytic behavior tuning via structural modifications of silylated‐diphosphine Ni(II) complexes for ethylene selective dimerization

“…Any increase (Table 5, entries 3, 4, 7, 8, 12, 15, and 16) or decrease (Table 5, entries 1, 5, 9, 10, and 13) in the concentration of DEAC may lead to a decrease in catalytic activity. A low concentration of DEAC may unable to completely activate the catalytic system [ 20,33 ] while a higher concentration may cause over‐reduction and deactivate the catalytic system. [ 34 ] The highest catalytic activity of 1.29 × 10 8 g (mol Ni ) ‐1 h ‐1 was obtained by precatalyst 1 at 500 equiv DEAC (Table 5, entry 2).…”

“…Ligands L 5 and L 6 were prepared according to the method established by our group. [ 20 ] The preparation methods for L 1 – L 4 and the structures of L 5 and L 6 are illustrated in Scheme 2 (for detailed synthesis procedures of L 1 – L 6 see the Supporting Information).…”

“…[32] Highest temperature screening provides the lowest C 4 selectivity, it enhances the formation of C 6 products at the expense of the C 4 fraction (Table 4, Changing the cocatalyst molar ratio in the oligomerization reaction can tune the catalytic environment and therefore influence the catalytic performance. [20,22] Probing the role of DEAC by changing its molar ratio suggested that the concentration of cocatalyst significantly influences the catalytic activity and C 4 selectivity ( Table 5). The precatalysts 1, 2, and 4 offer high catalytic activity at 500 equiv DEAC (Table 5, entries 2, 6, 14), while precatalyst 3 exhibited the highest activity at 700 equiv DEAC ( Table 5, entry 11).…”

“…[ 19 ] Our group recently established that the Ni(II) complexes of silicon‐bridged ligands can offer excellent catalytic performance for selective ethylene dimerization (Scheme 1). The Ni(II) complexes based on PCSiP ( A ), [ 20 ] silicon‐bridged PNP ( B ), [ 21 ] and silylated‐PNP ( C ) [ 22 ] ligands have been shown to be efficient dimerization catalysts that can provide as much as 2.40 × 10 8 g (mol Ni ) ‐1 h ‐1 high catalytic activity (in the case of B ) and more than 97% C 4 selectivity (in the case of A ).…”

Chromium catalysts based on PNP(NR2)2 ligands for selective ethylene oligomerization

“…We recently found that the ligands having PNP scaffolds such as PNSiP, PNSiCP, and PN (CH 2 ) n P behave as efficient catalytic systems for selective ethylene tri-/ tetramerization. [13][14][15][16][17][18] To further elucidate the potential role of the PNP scaffold toward ethylene oligomerization, we, herein, reported three new PNP-based L 1 -L 3 ligands with PNP (NR 2 ) 2 scaffold, which upon coordination with CrCl 3 (THF) 3 correspondingly afforded 1-3 chromium complexes (Scheme 1). Upon activation with MMAO-3A, the 1-3 complexes when scrutinized for ethylene oligomerization offered efficient catalysts for selective ethylene tri-/tetramerization.…”