Cobalt(II), nickel(II) and zinc(II) coordination chemistry of the N, N′-disubstituted hydroxylamine-(diamido) ligand, 3, 3′-(hydroxyazanediyl)dipropanamide. (1st September 2018)

• Record Type: Journal Article
• Authors: Papanikolaou, Michael G.; Hadjithoma, Sofia; Miras, Haralampos N.; Keramidas, Anastasios D.; Kabanos, Themistoklis A.
• Is Part Of: Polyhedron. Volume 151(2018)
• Page Start: 417
• Page End: 425
• Publication Date: 2018-09-01
• Subjects: Hydroxylamines -- NMR -- HR-MS -- X-ray structure -- UV–Vis; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2018.06.002
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: The hydroxylamine ligand 3, 3′-(hydroxyazanediyl)-dipropanamide (Hhydia) forms stable complexes with cobalt(II), nickel(II) and zinc(II) ions, coordinating in its neutral form in a tridentate O, N, O mode via the hydroxylamine nitrogen atom and the two carbonyl oxygen atoms. The NMR spectra of Zn II -Hhydia and the UV–Vis spectroscopy of the Co II -Hhydia complexes reveal the co-existence of both the 1:1 and 1:2 metal:ligand species in solution, while the UV–Vis spectroscopy of the Ni II -Hhydia complex shows the existence of only 1:2 [Ni II (Hhydia)2 ] 2+ species. HR-MS provide additional evidence for these observations. Abstract: Although directly relevant to metal mediated biological nitrification and the coordination chemistry of peroxide, the transition metal complexes of hydroxylamines and their functionalized variants remain mainly unexplored except vanadium(V) and molybdenum(VI). Reaction of the chelating hydroxylamine ligand 3, 3′-(hydroxyazanediyl)dipropanamide (Hhydia) with [M II (CH3 COO)2 ]· x H2 O (M = Co II, Zn II ) in methyl alcohol solution yields the complexes [Co II ( η 1 : η 1 -CH3 COO)( η 1 -CH3 COO)(Hhydia)], (1 ) and [Zn II ( η 1 -CH3 COO)2 (Hhydia)], (4 ), while reaction of Hhydia with trans -[Ni II Cl2 (H2 O)4 ]·2H2 O yields [Ni II (Hhydia)2 ]Cl2 (3 ). The X-ray structure analysis of 1 and 4 revealed that the Co II and Zn II atoms are bonded to a neutral tridentate O, N, O -Hhydia ligand and a chelate and a monodentate acetate groups in a severely distorted octahedral geometry for 1 and two monodentate acetate groups for 4 in a highly distorted trigonal bipyramidal geometry ( τ = 0.63). The X-ray structure analysis of 3 revealed that the nickel atom in [Ni II (Hhydia)2 ] 2+ is bonded to two neutral tridentate O, N, O -Hhydia ligands. The twist angle, θ, in [Ni II (Hhydia)2 ] 2+ is 55.1(2)°, that is, very close to an ideal octahedron. The metal/Hhydia complexes were studied by UV–Vis (cobalt and nickel compounds), NMR (zinc compounds), HR-MS spectroscopy. The 1 H and 13 C NMR spectra of the methyl alcohol or acetonitrile solutions of Zn II -Hhydia complexes show the existence of both the 1:1 and 1:2 metal:ligand species being in dynamic equilibrium. The exchange processes between the Zn II -Hhydia is through complete dissociation-association of the ligand from the complexes as it is evident from the 2D { 1 H} EXSY NMR spectroscopy. UV–Vis spectroscopy of the Co II -Hhydia in methyl alcohol also shows the existence of both the 1:1 and 1:2 metal:ligand species in contrast to 1:2 complex [Ni II (Hhydia)2 ] 2+ which is the only species found in solution. The NMR and UV–Vis observations are additionally supported by the HR-MS studies.