Synthesis of cubane-type Ni(II) complexes from pyridyl-alcohol ligands; their single-molecule magnet behaviour
Résumé
The reactions of NiCl2 center dot 2H(2)O or [NiCl2(DME)] (DME = dimethoxyethane) with 2-methyl-1-(pyridin-2-yl)-propan-2-ol (HL) and 2-(pyridin-2-yl) ethanol (HLEt), in a 1 : 1 ratio, afforded the tetranuclear, cubane-type clusters [Ni(mu(3)-Cl)Cl(HL)](4) (3) and [Ni(mu(3)-Cl) Cl(HLEt)](4) (4), respectively. These are tetramers of the hypothetical mononuclear formula-isomers [NiCl2(HL)] and [NiCl2(HLEt)], respectively, and represent rare examples of structurally characterized cubane-like transition metal dihalogenide complexes. The 2 : 1 reactions between HL or HLEt and [NiCl2(DME)] yielded, instead, the mononuclear [NiCl2(HL)(2)] (1) and the dinuclear complex [Ni(mu-Cl)(HLEt)(2)](2)Cl-2 (2), respectively. The reaction of 3 with NaOH afforded selectively the cubane-type cluster [Ni(mu(3)-OH)Cl(HL)](4) (5) which differs only in the nature of the capping anions (Cl vs. OH, respectively). The magnetic properties of the unusual tetranuclear cubanes 3 and 5 have been investigated and revealed in both cases single-molecule magnet (SMM) behaviour.