The synthesis, crystallographic and magnetic characterization of di- and tri-nuclear Ni(II) and Co(II) complexes of (2-sulfanylphenyl)bis(pyrazolyl)methane

The synthesis of a trinuclear thiolate bridged Ni-II system, [Ni-3(L5S)(4)](2+) [L5SH = (2-sulfanylphenyl)bis(pyrazolyl)methane] which contains a linear NiS2NiS2Ni moiety, is reported. Two octahedrally coordinated (L5S)(2)Ni complexes, in which the thiol sulfurs are mutually cis, constitute the two terminal positions while the central position contains a distorted tetrahedral, four-coordinate, Ni(II) ion. In the presence of alkyl- or aryl-nitriles, such as MeCN, the [Ni-3(L5S)(4)](2+) cation undergoes cleavage and rearrangement reactions to give thiolate bridged dinuclear dications, either [Ni-2(L5S)(2)(MeCN)(4)](2+) or [Ni-2(L5S)(2)(MeCN)(2)(H2O)(2)](2+), in which MeCN ligand N-donors (and/or H2O O-donors) occupy the vacant coordination sites of each Ni2+ atom. An analogous Co(II) dimer is also reported. The trimer --> dimer reaction can be reversed by desolvation of [Ni-2(L5S)(2)(MeCN)(4)](2+) or [Ni-2(L5S)(2)(MeCN)(2)(H2O)(2)](2+) by an appropriate non-nitrile solvent, such as MeNO2 resulting in reformation of the [Ni-3(L5S)(4)](2+) cation. Variable temperature magnetic data indicate that the Ni atoms in the trimer are weakly antiferromagnetically coupled while they are weakly ferromagnetically coupled in the dimer.