Weak Interactions Modulating the Dimensionality in Supramolecular Architectures in Three New Nickel(II)-Hydrazone Complexes, Magnetostructural Correlation, and Catalytic Potential for Epoxidation of A

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• 作者：Dipali Sadhukhan ; Aurkie Ray ; Guillaume Pilet ; Corrado Rizzoli ; Georgina M. Rosair ; Carlos J. Go虂mez-Garci虂a ; Sandra Signorella ; Sebastia虂n Bellu虂 ; Samiran Mitra
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：September 5, 2011
• 年：2011
• 卷：50
• 期：17
• 页码：8326-8339
• 全文大小：1301K
• 年卷期：v.50,no.17(September 5, 2011)
• ISSN：1520-510X

文摘

Three different ONO donor acetyl hydrazone Schiff bases have been synthesized from the condensation of acetic hydrazide with three different carbonyl compounds: salicylaldehyde (HL¹), 2-hydroxyacetophenone (HL²), and 2, 3-dihydroxybenzaldehyde (HL³). These tridentate ligands are reacted with Ni(OOCCF₃)₂路xH₂O to yield three new Ni(II) complexes having distorted octahedral geometry at each Ni center: [Ni(L¹)(OOCCF₃)(CH₃OH)]₂ (1), [Ni(L²)(OOCCF₃)(H₂O)]₂ (2), and [Ni(L³)(L³H)](OOCCF₃)(H₂O)_1.65(CH₃OH)_0.35 (3). The ligands and the complexes have been characterized by elemental analysis and IR and UV鈥搗is spectroscopy, and the structures of the complexes have been established by single crystal X-ray diffraction (XRD) study. 1 and 2 are centrosymmetric dinuclear complexes and are structural isomers whereas 3 is a bis chelated cationic monomer coordinated by one neutral and one monoanionic ligand. O鈥揌路路路O hydrogen bonds in 3 lead to the formation of a dimer. Slight steric and electronic modifications in the ligand backbone provoke differences in the supramolecular architectures of the complexes, leading to a variety of one, two, and three-dimensional hydrogen bonded networks in complexes 1鈥?b>3 respectively. Variable temperature magnetic susceptibility measurements reveal that moderate antiferromagnetic interactions operate between phenoxo bridged Ni(II) dimers in 1 and 2 whereas very weak antiferromagnetic exchange occurs through hydrogen bonding and 蟺鈥撓€ stacking interactions in 3. All complexes are proved to be efficient catalysts for the epoxidation of alkenes by NaOCl under phase transfer condition. The efficiency of alkene epoxidation is dramatically enhanced by lowering the pH, and the reactions are supposed to involve high valent Ni^III鈥揙Cl or Ni^III鈥揙路 intermediates. 3 is the best epoxidation catalyst among the three complexes with 99% conversion and very high turnover number (TON, 396).