Use of the sulfato ligand in 3d-metal cluster chemistry: A family of hexanuclear nickel(11) complexes with 2-pyridyl-substituted oxime ligands

The initial use of 2 -pyridyl- substituted oximes [(py)C(R)-NOH; R = Me, Ph]/sulfate blend in nickel(II) chemistry has yielded a family of hexanuclear clusters. The syntheses, structures and magnetic properties are reported of [Ni-6(SO4)(4)-(OH){(py)C(Me)NO}(3){(py)C(Me)NOH}(3)(MeOH)(2)(H2O)] (1), [Ni-6(SO4)(4)(OH){(py)C(ph)NO)(3)}(py)C(ph)NOH)(3)(MeOH)(3)] (2) and [Ni-6(SO4)(4)(OH){(py)C(ph)NO)(3)}(py)C(ph)NOH)(3)(H2O)(3)] (3), where (py)C(Me)NOH is methyl 2-pyridyl ketone oxime and (py)C(ph)NOH is phenyl 2-pyridyl ketone oxime. The hexanuclear molecules present in the three complexes have similar structures which contain the [Ni-6(mu(3)-OH)(mu(3)-SO4)(3)(mu(3)-ONR)(3)](2+) core. The core consists of six Ni-II ions arranged as two parallel equilateral triangular subunits, one small (Ni center dot center dot center dot Ni ca. 3.3 angstrom) and the other larger (Ni center dot center dot center dot Ni ca. 6.0 angstrom). Characteristic IR bands are discussed in terms of the known structures of 1-3. The magnetic properties of 1 and 2 have been studied by variable-temperature dc magnetic susceptibility techniques which indicate antiferromagnetic interactions. A simple 2-J model was found to be adequate to describe the similar thermal variation of the molar magnetic susceptibilities of 1 and 2. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007.