Nickel(II) complexes of bidentate N-N' ligands containing mixed pyrazole, pyrimidine and pyridine aromatic rings as catalysts for ethylene polymerisation

• Type: Article in International Scientific Journal
• Date: 2015

Authors

Belen Moreno-Lara (Author) Other; Sónia A. Carabineiro (Author) FEUP; Paramasivam Krishnamoorthy (Author) Other; Ana M. Rodríguez (Author) Other; João F. Mano (Author) Other; Blanca R. Manzano (Author) Other; Felix A. Jálon (Author) Other; Pedro T. Gomes (Author) Other

Journal

Title: Journal of Organometallic Chemistry

No. 799-800

Pages: 90-98

ISSN: 0022-328X

Publisher: Elsevier

Indexing

ISI Web of Knowledge

ISI Web of Science

Scopus

Associated Projects

LSRE-LCM - Laboratório de Processos de Separação e Reação - Laboratório de Catálise e Materiais

Other information

DOI: 10.1016/j.jorganchem.2015.09.004

Abstract (EN): This work describes the synthesis and characterisation of Ni(II) complexes of the following neutral bidentate nitrogen ligands containing pyrazole (pz), pyrimidine (pm) and pyridine (py) aromatic rings: 2- pyrazol-1-yl-pyrimidine (pzpm), 2-(4-methyl-pyrazol-1-yl)-pyrimidine (4-Mepzpm), 2-(4-bromo-pyrazol-1-yl)-pyrimidine (4-Brpzpm), 2-(3,5-dimethyl-pyrazol-1-yl)-pyrimidine (pz*pm), 2-pyrazol-1-ylpyridine (pzpy) and bis(3,5-dimethylpyrazol-1-yl)phenylmethane (bpz*mph). The complexes [NiBr2(pzpm)] (1), [NiBr2(4-Mepzpm)] (2), [NiBr2(4-Brpzpm)] (3), [NiBr2(pz*pm)] (4), [NiBr2(pzpy)] (5) and [NiBr2(bpz*mph)] (6) were tested as catalysts for ethylene polymerisation, in the presence of the cocatalysts methylaluminoxane (MAO) or diethylaluminium chloride (AlEt2Cl), the catalyst systems 1-3/ MAO showing moderate to high activities up to the temperature of 20 C only in the presence of MAO, whereas 4-6/MAO revealed to be inactive. Other related Pd(II) complexes, already reported in previous works, such as [PdClMe(pzpm)], [PdClMe(pz*pm)], [PdClMe(pzpy)] and [PdClMe(bpz*mph)], also showed to be inactive in the polymerisation of ethylene, when activated by MAO or AlEt2Cl. Selected samples of polyethylene products were characterised by GPC/SEC, 1 H and 13C NMR and DSC, showing to be low molecular weight polymers with Mn values ranging from ca. 550 to 1500 g mol1 and unusually low dispersities of 1.2e1.7, with total branching degrees generally varying between 2 and 12%, melting temperatures from 40 to 120 C and crystallinities from 40 to 70%.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9