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

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(NO3)2 is used as the nickel source; it is possible, however, to add a second
nickel if NiCl2 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.
Ni2(L1)Cl4(DMF)2.DMF:  orthorhombic, P212121, a = 12.2524(11) Å, b = 16.6145(15) Å, c = 20.1234(19) Å, V =
4096.5(6) Å3, Z = 4. [Ni2(L2)Cl4(DMF)]2·2DMF:  triclinic, P-1, a = 12.5347(5) Å, b = 12.5403(5) Å, c = 14.3504(6) Å, α = 67.348(1)°, β = 69.705(1)°, γ = 81.549(1)°, V = 1952.25(14) Å3, Z = 1. Ni(L2)·(NO3)2:  monoclinic,
P21/n, a = 9.6738(3) Å, b = 30.2229(9) Å, c = 15.8238(5) Å, β = 97.995(1)°, V = 4581.4(2) Å3, Z = 8.