Cobalt complexes based on 2-(1H-benzimidazol-2-yl)-phenol derivatives: preparation, spectral studies, DFT calculations and catalytic behavior toward ethylene oligomerization. Issue 11 (3rd June 2017)

• Record Type: Journal Article
• Authors: Haghverdi, Marzieh; Tadjarodi, Azadeh; Bahri-laleh, Naeimeh; Nekoomanesh Haghighi, Mahdi
• Is Part Of: Journal of coordination chemistry. Volume 70:Issue 11(2017)
• Page Start: 1800
• Page End: 1814
• Publication Date: 2017-06-03
• Subjects: Benzimidazolylphenols -- cobalt(II) complexes -- characterization -- DFT calculations -- ethylene oligomerization; Coordination compounds -- Periodicals; 541.2242
• DOI: 10.1080/00958972.2017.1328506
• Languages: English
• ISSNs: 0095-8972

Abstract

Abstract: In this study, five novel Co(II) complexes of 2-(1 H -benzimidazol-2-yl)-phenol derivatives (HLx : x = 1–5) have been synthesized and characterized. The general formula for complexesC1 andC2 is K2 [Co(HL1, 2 )2 Cl2 ]·H2 O, for complexC3 K2 [Co(HL3 )2 Cl2 ], and for complexesC4 andC5 [Co(HL4, 5 )2 ]. In all complexes, the ligands are coordinated as bidentate, via one imine nitrogen and the phenolate oxygen atoms. The structures of the compounds were characterized by FT-IR, UV–vis, 1 H, 13 C NMR spectroscopies, ICP and elemental analysis (C, H, and N). The purity of these compounds was ascertained by melting point (m.p.) and TLC. Geometry optimization of the studied complexes was done by Gaussian09 software at B3LYP/TZVP level of theory and satisfactory theoretical–experimental agreement was achieved for NMR and IR spectra of the compounds. Based on the combined experimental and theoretical studies, six-coordinate octahedral structures have been proposed for complexesC1 –C3, while complexesC4 andC5 had distorted tetrahedral geometry. All complexes were activated with diethylaluminum chloride (Et2 AlCl), cobalt(II) complexes containing bulky methyl groups in the aryl moiety show high catalytic activities (1774 kg∙mol −1 (Co)∙h −1 ) for ethylene oligomerization. The oligomers obtained from the cobalt complexes exhibit good selectivity for linear 1-butene and 1-hexene. Results revealed that both the steric and electronic effects of ligands strongly affect the catalytic activities and the properties of the catalytic products. Abstract :