[Cr(III)(8)Ni(II)(6)](n+) Heterometallic Coordination Cubes

Three new heterometallic [Cr(III)(8)Ni(II)(6)] coordination cubes of formulae [Cr(III)(8)Ni(II)(6)L(24)(H(2)O)(12)](NO(3))(12) (1), [Cr(III)(8)Ni(II)(6)L(24)(MeCN)(7)(H(2)O)(5)](ClO(4))(12) (2), and [Cr(III)(8)Ni(II)(6)L(24)Cl(12)] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [Cr(III)L(3)] and the corresponding Ni(II) salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight Cr(III) and six Ni(II) ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the Cr(III) and Ni(II) ions, with J(Cr-Ni) = + 0.045 cm(−1). EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the Cr(III) ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both Cr(III) and Ni(II) ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)–(3) join the previously published, structurally related family of [M(III)(8)M(II)(6)] cubes, where M(III) = Cr, Fe and M(II) = Cu, Co, Mn, Pd.