Two nickel(II) complexes exhibiting 'fused' 9-MC-3 and 12-MC-4 metallacrowns

The reactions of (E)-quinoline-2-carbaldehyde oxime (Hqcah) with Ni(ClO4)2·6H2O and NH4SCN and with Ni(CF3SO3)2 and NaN3 led to two solitary metallacrowns (MCs) ([Ni5(qcah)7(Hqcah)(CH3OH)(SCN)(OH)]·ClO4 (1) and [Ni4(qcah)4(N3)4(Py)4] (2), respectively. Complex 1 is a pentanuclear nickel cluster that exhibits two "fused" 9-MC-3 structural units with both rings possessing Ni2–N–O–Ni1–N–O–Ni5–O–N and Ni3–N–O–Ni4–O–Ni5–O–N connectivities. Complex 2 consists of four [Ni(qcah)(N3)(Py)] units with adjacent nickel atoms linked together through N–O groups to construct a tetranuclear 12-MC-4 metallacrown. The ligands exhibit μ3:η2:η1:η1, μ2:η2:η1 and μ1:η2 coordination modes in 1 and μ2:η2:η1 coordination mode in 2. Magnetic property measurements and the fitting of various temperature magnetic susceptibilities revealed antiferromagnetic coupling between metal centers with the negative coupling parameters in both 1 and 2.