Pyrazolyl‐phosphinoyl nickel (II) complexes: synthesis, characterization and ethylene dimerization studies

Abstract

A series of new nickel (II) complexes of general formula [NiBr 2 (N,O) 2 ] (Ni1-Ni5) based on bidentate pyrazolyl-phosphinoyl ligands were prepared and characterized by IR spectroscopy, elemental analysis, high-resolution mass spectrometry (HRMS), and X-ray crystallography for Ni1. X-ray crystallographic analyses of Ni1 revealed a six-coordinate species, in which Ni (II) lies in an octaedral environment. The nickel center is chelated by two pyrazolyl-phosphinoyl ligands with the two bromide ligands occupying mutually trans positions. Upon activation with methylaluminoxane (MAO), all nickel complexes were able to oligomerize ethylene with turnover frequencies (TOFs) varying from 5.0 to 16.6 × 10 3 (mol ethylene) (mol Ni) −1 h −1 producing selectively 1-butene (91.0-95.5 wt%). The substitution on the pyrazolyl group and the length of the backbone chain play a significant role in the catalytic activity. The use of MAO/TMA (1:1) or MAO/TiBA (1:1) instead of MAO drastically reduced the activities. The TMA content has no significant influence on the selectivity. However, the use of TiBA leads to a reduction of 1-butene (from 94.9 to 71.0 wt%) and an improvement in the hexene production (from 1.5 to 23.3 wt%). Under optimized reaction conditions (10°C, 20 min, 20 bar ethylene, [Al/Ni] = 600), Ni1/MAO catalytic system yielded TOF = 24.7 × 10 3 (mol ethylene) (mol Ni) −1 h −1 with good selectivities for α-C4 (94.9 wt%).

Novel zinc (II) and nickel (II) complexes of a quinazoline‐based ligand with an imidazole ring: Synthesis, spectroscopic property, antibacterial activities, time‐dependent density functional theory calculations and Hirshfeld surface analysis

“…The coordination environment of Ni 2+ formed by three imidazole rings nitrogens (N4/N7/N11) and three nitrogen oxides oxygens (O1/O2/O3) were distorted octahedral configuration. All Ni–N/O bond lengths were within the scope of 2.048(3)–2.126(2) Å, which were consistent with relevant literature [ 37,38 ] As shown in Figure 4c, the dihedral angle between the planes of O2–Ni1–N4 and O1–Ni1–N7 was 86.379°, which was further confirmed the distorted geometry.…”

“…X-ray diffraction showed that 2 crystallized to triclinic space group P-1. The independent unit comprises a Ni complex with three chelating L and two non- 2) Å, which were consistent with relevant literature [37,38] As shown in Figure 4c, the dihedral angle between the planes of O2-Ni1-N4 and O1-Ni1-N7 was 86.379 , which was further confirmed the distorted geometry. The interactions of hydrogen bonds and weak C-HÁÁÁπ (Ph) were discovered in Figure 5 and Tables S3 and S4.…”

Synthesis, spectroscopic studies, and single‐crystal structures of two 3‐D supramolecular zinc(II) and nickel(II) complexes containing thiazole ring: Antimicrobial assays, time‐dependent density functional theory calculations, and Hirshfeld surface analysis

“…All Ni-N/O parameters were within the scope of 2.0586( 16)-2.0892( 14) Å, which were in correspondence with the reported values. [36,37] The dihedral angle between the planes of N1-Ni-O2 and O1-Ni-O1 was 86.379 , constituting a distorted octahedral geometry.…”

Ni-Based Complexes in Selective Ethylene Oligomerization Processes

“…Casagrande and co-workers developed highly-selective for 1-butene catalytic systems based on pyrazolyl-phosphinoyl nickel(II) complexes (50, Figure 39) [85]. n = 1,2; R 1 = H, Me, Ph; R 2 , R 3 In [86] bis(pyrazolyl)methane nickel(II) complex was studied as pre-catalysts for ethylene dimerization (51, Figure 40).…”

“…Casagrande and co-workers developed highly-selective for 1-butene catalytic systems based on pyrazolyl-phosphinoyl nickel(II) complexes (50, Figure 39) [85]. With an increase in the size of a substituent at pyrazole ring-upon transition from Me to Ph (Figure 38)-the activity decreases from 13 × 10 3 to 10 × 10 3 h −1 [84].…”