Tripodal Thiols as Ligands for Molecular Magnets: Very Strong Antiferromagnetic Exchange Interactions in Vanadium(III) Clusters

The synthesis, structural and magnetic characterisation of [(V3O)-O-III-(tmme)(2)(diimine)(2)Cl] [diimine =2,2'-bipyridine (1) or 1,10-phenanthroline (2)] and (HNEt3)(2)[(V4O)-O-III(tmme)(4)] (3) is reported, in which H(3)tmme is tris(mercaptomethyl)ethane, MeC(CH2SH)(3), the thiol analogue of the famous tripodal alcohol ligands typified by H(3)thme [tris(hydroxymethyl)ethane, MeC-(CH2OH)(3)]. Complexes 1 and 3 have "T-shaped" and square topologies, respectively, and the latter is centred on a rare example of a square-planar oxide. The tri-thiolate ligands bind the periphery of the clusters and provide such strong antiferromagnetic exchange pathways that in both cases only a single total spin state is occupied up to room temperature, in the absence of metal metal bonding. Magnetic data, electronic structure calculations and electrochemical data are reported.