360071-92-7Relevant academic research and scientific papers
Synthesis, structures and ethylene polymerisation behaviour of low valent β-diketiminato chromium complexes
Gibson, Vernon C.,Newton, Claire,Redshaw, Carl,Solan, Gregory A.,White, Andrew J. P.,Williams, David J.
, p. 1895 - 1903 (2007/10/03)
The preparation, reaction chemistry and ethylene polymerisation behaviour of low valent β-diketiminato chromium complexes are described. [(DDP)CrCl(μ-Cl)]2 (1) [DDPH =2-{(2,6-diisopropylphenyl)amino}-4-{(2,6-diisopropylphenyl)imino} -pent-2-ene] is formed by treatment of CrCl3(THF)3 with LiDDP. Alkylation of 1 with AlMe3 results in the formation of the binuclear dimethyl complex [(DDP)CrMe(μ-Cl)]2 (2). In contrast the attempted alkylation of 1 with benzylmagnesium chloride results in reduction to form the dichromium(II) complex [(DDP)Cr(μ-Cl)]2 (3). Depending on the conditions of crystallisation, 3 can be obtained as the THF adduct [3(THF)2·THF] or co-crystallised with a molecule of dibenzyl [3·Bz-Bz]. Cleavage of the dimeric unit in 1 can be achieved by the addition of carboxylates or β-diketonates to give [(DDP)CrCl(O2CR)(THF)] (R = Me 4a, Ph 4b) and [(DDP)CrCl({O(R)C}2CH)] (R = Me 5a, Ph 5b), respectively. Single crystal X-ray diffraction studies have been performed on 1, 2, 3(THF)2·THF, 3·Bz-Bz, 4a, and 5b. Complexes 1, 2 and 3(THF)2·THF are dimeric and have molecular C2h symmetry. Complex 3·Bz Bz is also dimeric but has its potential C2h symmetry removed by a significant tetrahedral distortion of the chromium coordination geometry. Compound 4a has an octahedral chromium centre coordinated to a single bidentate diketiminate ligand, a bidentate acetate, a chloride and a THF molecule. Complex 5b has a square pyramidal chromium with apical chloride and basal η2 diketiminate and diketonate ligands. The complex contains strong intramolecular C-H···π stabilising interactions. All the complexes are active in ethylene polymerisation on treatment with suitable aluminium activators, affording high molecular weight polyethylene.
