Anion-Controlled Nuclearity in Nickel Complexes with Potentially Dinucleating, Poly(oxime) Amine Ligands

Abstract

Two new ligands consisting of bis(oxime) amine units tethered by a bridge have been synthesized. Their nickel chloride and nickel nitrate complexes have also been synthesized and characterized by X-ray crystallography, FTIR, mass spectrometry, and elemental analysis. One of these ligands, L1 (N,N,N',N'-tetra(1-propan-2-onyl oxime)-diamino-m-xylene), is always dinucleating, while the other ligand, L2 (N,N,N',N'-tetra(1-propan-2-onyl-oxime)-1,3-diaminopropane), shows an unusual anion dependence on the nuclearity. When nickel chloride is used, the ligand acts in a dinucleating manner and coordinates two nickels; however, when nickel nitrate is used, the ligand acts in a monodentate fashion and coordinates only one nickel. Once the mononuclear complex is formed, it is not possible to add a second nickel if Ni(NO(3))(2) is used as the nickel source; it is possible, however, to add a second nickel if NiCl(2) is used as the nickel source. The dinuclear complex can be converted to the mononuclear one by either using silver nitrate to exchange the chloride anions for nitrates or by dissolving the complex in water. Ni(2)(L1)Cl(4)(DMF)(2).DMF: orthorhombic, P2(1)2(1)2(1), a = 12.2524(11) A, b = 16.6145(15) A, c = 20.1234(19) A, V = 4096.5(6) A(3), Z = 4. [Ni(2)(L2)Cl(4)(DMF)](2).2DMF: triclinic, P-1, a = 12.5347(5) A, b = 12.5403(5) A, c = 14.3504(6) A, alpha = 67.348(1) degrees , beta = 69.705(1) degrees , gamma = 81.549(1) degrees , V = 1952.25(14) A(3), Z = 1. Ni(L2).(NO(3))(2): monoclinic, P2(1)/n, a = 9.6738(3) A, b = 30.2229(9) A, c = 15.8238(5) A, beta = 97.995(1) degrees , V = 4581.4(2) A(3), Z = 8.

Redox Potentials and Protonation of the A-Cluster from Acetyl-CoA Synthase. A Density Functional Theory Study

“…One can note a very long Ni p –Fe1 distance of 3.574 Å in the optimized structure of A red2 . The calculated Ni p –H 2 O bond length in A ox is 2.067 Å, which is shorter than the 2.32 Å value from EXAFS; on the other hand, the calculated value is in the range of bond distances characteristic for nickel complexes with water ligands. − The valence angles around Ni p (S6–Ni p –S5, S6–Ni p –S1, S1–Ni p –S5, Table ) reveal that the proximal nickel atom in A ox has a planar coordination sphere, similarly to the experimental data (Table ). In the A red1 the changes in valence angles show a distorted planar coordination, whereas in the A red2 the proximal nickel atom has a tetrahedral coordination sphere.…”

Ligand-controlled nuclearity in nickel bis(benzimidazolyl) complexes

“…Examples reported in the literature have shown that the nuclearity of metal complexes can be controlled by counter ions or by supporting ligands. [14][15][16] Baldwin and co-workers demonstrated that a dinuclear nickel species could be obtained with a coordinated anion, and the utilization of an innocent anion caused the formation of a mononuclear complex. 14 Shimazaki et al have shown that if a sterically hindered ligand is employed in the preparation of the nickel complex, a mononuclear species is formed instead of a dinuclear compound.…”

“…[14][15][16] Baldwin and co-workers demonstrated that a dinuclear nickel species could be obtained with a coordinated anion, and the utilization of an innocent anion caused the formation of a mononuclear complex. 14 Shimazaki et al have shown that if a sterically hindered ligand is employed in the preparation of the nickel complex, a mononuclear species is formed instead of a dinuclear compound. 16 Herein we wish to report a series of nickel complexes supported by a tripodal bis-methylbenzimidazolyl ligand and their characterization by mass, infrared, and electronic absorption spectroscopies and X-ray crystallography.…”

{μ-N,N′-Bis[1-(2-pyridyl)ethylidene]benzene-1,2-diamine}di-μ-chlorido-bis[diaquanickel(II)] dichloride ethanol disolvate

“…The Ni•••Ni distance spanned by the two chloride ion bridges is 3.9615 (16) Å. The Ni-Cl distances in (I) are longer than distances observed in other Ni II coordination complexes (Li et al, 2005;Deters et al, 2005;Sengottuvelan et al, 2008). Two chloride ions are present in the asymmetric unit to compensate for the doubly positive charge of the complex and hydrogen bonds (Table 2) help to establish the packing.…”