Novel topologies in NiII cluster chemistry: Incorporation of alkaline-earth metals in the new [NiII6MgII2] and [NiII8MII] (M = Sr, Ba) cages

Abstract

The reaction of the complex [Ni₂(H₂O)(piv)₄(Hpiv)₄] (1) (Hpiv = pivalic acid) with Hppo (3-phenylpyrazolin-5-one) in the presence of a base of an alkaline-earth metal (M^II = Mg^II, Sr^II or Ba^II) has led to three different Ni^II clusters whose structures are controlled by the nature of M^II. The formulae of the new heteronuclear cages are [Ni₆Mg₂(OH)₂(ppo)₄(piv)₁₀(Hppo)₄(MeOH)₂] (2), [Ni₈Sr(OH)₂(ppo)₆(piv)₁₀(Hppo)₅(Hpiv)₂(MeCN)] (3) and [Ni₈Ba(OH)₂(ppo)₆(piv)₁₀(Hppo)_5.3(Hpiv)_0.7(MeCN)₂] (4). Magnetic measurements indicate that the spin ground state of 2 consists of two independent S = 3 units, while the presence of two non-interacting S = 2 fragments in the molecule is postulated for compounds 3 and 4.