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

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 (MII= MgII, SrII or BaII) has led to three different NiII clusters whose structures are controlled by the nature of MII. 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.