Synthesis and characterisation of new Ni2Mn, Ni2Mn2 and Mn8 clusters by the use of 2-pyridyl oximes

Abstract

The initial employment of methyl 2-pyridyl ketoxime, (py)C(Me)NOH, in mixed metal Ni/Mn cluster chemistry, provided access to complexes [NiII2MnIII{(py)C(Me)NO}6](ClO4) (1) and [NiII2MnIII2{(py)C(Me)NO}6(OMe)2(MeOH)2](ClO4)2 (2) that display a linear and a zig-zag metal arrangement, respectively. 1 and 2 are synthesized by reacting Ni(ClO4)2·6H2O, (py)C(Me)NOH, Mn(ClO4)2·6H2O and NaOMe in different molar ratios (2:6:1:6, 1; 1:3:1:3, 2) in MeOH, and they are the first examples of 3d–3d′ mixed-metal clusters bearing (py)C(Me)NOH. The employment of phenyl 2-pyridyl ketoxime, (py)C(ph)NOH, instead of (py)C(Me)NOH, provided access to the octanuclear homometallic compound [MnII4MnIII4O4(NO3)2{(py)C(ph)NO}8(HCO2)2(MeOH)2] (3) that possesses a double-butterfly {MnII4MnIII4(μ4-O)2(μ3-O)2}12+ core. 3 joins the small family of Mn/(py)C(ph)NO− clusters. Variable-temperature, solid-state dc and ac magnetic susceptibility studies were carried out on 1 and 2 and revealed the presence of antiferromagnetic exchange interactions between the metal ions (JMn–Ni = −6.34 ± 0.14 cm−1 in 1;JMn–Ni = −4.57 ± 0.08 cm−1, JMn–Mn = −12.72 ± 0.12 in 2) and a diamagnetic ground state for both compounds.