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

Abstract

The synthesis of a trinuclear thiolate bridged Ni^II system, [Ni₃(L5S)₄]²⁺ [L5SH = (2-sulfanylphenyl)bis(pyrazolyl)methane] which contains a linear NiS₂NiS₂Ni moiety, is reported. Two octahedrally coordinated (L5S)₂Ni 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 [Ni₃(L5S)₄]²⁺ cation undergoes cleavage and rearrangement reactions to give thiolate bridged dinuclear dications, either [Ni₂(L5S)₂(MeCN)₄]²⁺ or [Ni₂(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 [Ni₂(L5S)₂(MeCN)₄]²⁺ or [Ni₂(L5S)₂(MeCN)₂(H₂O)₂]²⁺ by an appropriate non-nitrile solvent, such as MeNO₂ resulting in reformation of the [Ni₃(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.