Synthesis, crystal structure and magnetic properties of a mononuclear and a ferromagnetically coupled dinuclear nickel(II) complex derived from a hexadentate Schiff base ligand

Reactions with NiII of a hexadentate Schiff base ligand, L, prepared from the reaction of 2-benzoylpyridine with N,N′-bis-(3-aminopropyl) ethylenediamine in the 2:1 molar ratio are reported. Mixing of this ligand with Ni(NO3)2 affords the mononuclear complex [NiL](NO3)2 (1), whereas the presence of NaN3 in the reaction system leads to the formation of the dinuclear complex [Ni2(L)(N3)4] (2). Both adducts have been characterized by X-ray crystallography revealing distorted octahedral NiN6 coordination environments around the NiII centers. The dinuclear complex contains terminal and end-on bridging azido ligands and displays Ni–N–Ni bridge angles of 101.1(2)° and 101.6(2)° and an intramolecular Ni⋯Ni separation of 3.330(1)Å. The μ-N3- bridges mediate ferromagnetic magnetic exchange interactions between the NiII centers of 2, leading to an S = 2 ground state. Fitting of bulk magnetization data provided the coupling constant J = +20.96 cm3 K mol−1 (in the H = −2JS1 · S2 convention for the Heisenberg Spin Hamiltonian), as well as the parameters g = 2.17, D = 0.69 cm−1 and TIP = 622 × 10−6 cm3 mol−1.

A hexadentate pyridyl/imine-based ligand capable of forming octahedral Ni(II) monomeric complexes stabilizes a bis-(end-on-azido) bridged dinuclear complex in the presence of azide. The dinuclear species is a novel example of ferromagnetically exchanged complex with S = 2 ground state.Figure optionsDownload as PowerPoint slide