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 [Ni-2(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.