A Tetrameric Nickel(II) “Chair” with both Antiferromagnetic Internal Coupling and Ferromagnetic Spin Alignment (original) (raw)

2001, Angewandte Chemie International Edition

Interest in polynuclear complexes of the 3d metals has been stimulated by the search for new magnetic materials [1, and by demonstration of the occurrence of oligonuclear metal centers in proteins such as urease. Of the relatively small number of reported tetranuclear complexes of S 1 nickel(ii) of known structure, the majority have a hemicubane-or ™butterfly-∫ rather than a squarelike core. [4] Of these molecules, just one is entirely antiferromagnetic, [5] while the remainder entail purely ferromagnetic interactions amongst the nickel(ii) ions. [6±10] Oximes have shown promise as bridging ligands for the preparation of polynuclear complexes. [11, 12] The reaction of 1,4,7-triazaheptane (diethylenetriamine, Dien) with the monooxime of 2,3-butanedione (ModaH) in the presence of Ni II ions, instead of yielding the anticipated Schiff base derivative, gave the tetranuclear Ni II compound 1 (dark brown crystals; C 4 H 8 O 2 1,4-dioxane), containing uncondensed but coordinated ketone and amine groups. Figure 1 a shows the structure of the the cation of 1, while Figure 1 b highlights its Ni II core. [{Ni(Dien)} 2 (m 3 -OH) 2 {Ni 2 (Moda) 4 }](ClO 4 ) 2 ¥ 2 C 4 H 8 O 2 ¥ 2 H 2 O 1