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Keywords:

  • Cluster compounds;
  • Hetero­metallic complexes;
  • Magnetic properties;
  • Transition metals

Abstract

The thiolato-bridged cobalt(II)/vanadium(II) complexes [Li(thf)4]2[Co2V(SPh)8] and [Li(15-crown-5)(thf)]2[Co2V(SPh)8] as well as a related nickel(II)/vanadium(II) complex [Li(15-crown-5)(thf)]2[Ni2V(SPh)8] have been prepared by treatment of CoCl2 (NiCl2) and VCl3 {[VCl3(thf)3]} with LiSPh in THF without and in the presence of 15-crown-5, respectively. The crystal structures of the trinuclear compounds were determined by X-ray analysis of single crystals and investigated by density functional theory. Both give evidence for one very short Ni–V distance (259.41 pm) in [Li(15-crown-5)(thf)]2[Ni2V(SPh)8]. The dark-coloured compounds display absorption bands over a wide energy range with an absorption onset lying in the near-infrared region at approximately 2000 nm. Magnetic measurements show strong antiferromagnetic coupling of the metal ions through acute phenylthiolate bridges (M–S–M < 76.1°). Ab initio multireference calculations together with mapping approaches reveal that the magnetic properties of the anionic metal complexes can be described by different effective spin Hamiltonians that indicate different types of intramolecular interactions between the metal ions. In [Co2V(SPh)8]2–, we found at low temperatures an effective S = 3/2 behaviour with small zero-field splitting (ZFS) caused by a strong, symmetric antiferromagnetic exchange interaction. A weak direct Ni–V bond in [Ni2V(SPh)8]2– generates an effective two-centre system that consists of an effective spin of S = 1/2 from the weakly bound Ni–V pair and a pseudospin S = 1 located on the other nickel site, antiferromagnetically coupled to an S = 1/2 ground state.