Versatile coordination behaviour of the chloro-tetrazine-picolylamine ligand: mixed-valence binuclear Cu( i )/Cu( ii ) complexes

Abstract : The 3-Cl-6-amino-(2′-picolyl)-1,2,4,5-tetrazine ligand HL1 has been synthesized and structurally characterized. Its versatile coordination behavior has been evidenced through reactions with Cu(Hfac)2 and Cu(triflate)2 precursors, which provided mixed-valence bimetallic Cu1.5Cu1.5 complexes [Cu2(μ-Cl)(L1)2] 2 and [Cu2(μ-triflate)(L1)2] 5. Changing the Cu(II) precursor and the solvent leads to the formation of mononuclear octahedral Cu(II) complexes [CuCl2(HL1)2]·2CH3CN 3 and [Cu(Hfac)2(HL1)] 4, in which only the amino-pyridine unit is involved in the coordination of the metal center. In contrast, in complexes 2 and 5, the ligands are deprotonated and bridge the metal centers as pyridine-amido-tetrazine fragments, while a bridging chloride or triflate ligand completes the coordination sphere of the metal ions. The Cu–Cu distances of 2.4313(4) Å in 2 and 2.5198(10) Å in 5 lie among the shorter values within mixed-valence bimetallic Cu complexes. Mixed-valence character is strongly supported by DFT calculations, showing the equal repartition of the unpaired electron between the two metal centers.
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Submitted on : Saturday, November 9, 2019 - 12:20:01 PM
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Oleh Stetsiuk, Svitlana Petrusenko, Lorenzo Sorace, Alexandru Lupan, Amr Attia, et al.. Versatile coordination behaviour of the chloro-tetrazine-picolylamine ligand: mixed-valence binuclear Cu( i )/Cu( ii ) complexes. Dalton Transactions, Royal Society of Chemistry, 2019, 48 (31), pp.11966-11977. ⟨10.1039/c9dt02379h⟩. ⟨hal-02357052⟩

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