Linked Nickel Metallacrowns from a Phosphonate/2-Pyridyloximate Blend of Ligands: Structure and Magnetic Properties

In
the present work, four new NiII clusters with nuclearities
ranging between Ni4 and Na2Ni8 were
synthesized, employing the versatile ligand phenylphosphonate and
6-methylpyridylaldoximate as the coligand. Crystallographic data show
that the tetranuclear complex [Ni4(6-MepaoH)4(PhPO3)2(OH)2(MeOH)4]­(OH)2 (1) consists of two dimers linked by phosphonate
bridges, whereas [Cs2Ni6(6-Mepao)6(PhPO3)3(OH)2(H2O)8] (2), Cs­[Ni8(6-MepaoH)6(6-Mepao)6(PhPO3)3]­(ClO4)5 (3), and [Ni8Na2(BzO)6(6-Mepao)6(PhPO3)3] (4) are built from phosphonato-linked {Ni3(6-Mepao)3} metallacycles. The [9-MCNiII(6‑Mepao)-3] fragments in 2–4 show the unusual coordination of additional Cs+, Na+, and/or NiII cations. Direct-current
magnetic measurements were carried in the 300–2 K range. Analysis
of the experimental data revealed a complex response with strong antiferromagnetic
interactions mediated by the oximato bridges and weak interactions
mediated by the phosphonate ones.