Synthesis, crystal structures and use in ethylene oligomerization catalysis of novel mono- and dinuclear nickel complexes supported by (E)-N′-(1-(thiophen-2-yl)ethylidene)benzohydrazide ligand

The coordination chemistry of NiII supported by (E)-N′-(1-(thiophen-2-yl)ethylidene)benzohydrazide ligand (HL) is reported and discussed. The crystal structure of ligand HL has been determined as well as those of three new NiII complexes (Ni(HL)2Br2, NiL2 and μ-aquo-Ni2L4). The pseudo-octahedral bis(chelate) Ni(II) complex 2 (NiL2), in which unexpected and singular Ni⋯S interaction is observed, was evaluated as catalyst for the oligomerization of ethylene and found to provide ethylene dimers and trimers as primary products with a turnover frequency (TOF) of 31 200 mol of C2H4 per mol. of Ni and per hour.

Graphical abstractSynthesis and crystal structure of the ligand (E)-N′-(1-(thiophen-2-yl)ethylidene)benzohydrazide (HL) and three new nickel complexes Ni(HL)2(Br)2, Ni(L)2 and Ni2(μ-H2O)(μ-L)2(L)2. Unexpected and totally original interaction Ni…S is observed in Ni(L)2 complex. The Ni(L)2 derivative is active in ethylene oligomerization in the presence of excess AlEtCl2.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis and structure of (E)-N′-(1-(thiophen-2-yl)ethylidene)benzohydrazide. ► Structures of three nickel complexes (2 mononuclear and 1 dinuclear) are described. ► Unexpected and original interaction Ni⋯S is observed in Ni(L)2 complex. ► Ni(L)2 is active in ethylene oligomerization in the presence of excess AlEtCl2.