Cyclopentadienylcobalt complexes containing sulfosalt units: synthesis and structure of [(C5Me4Et)3Co3AsS5]I and [(C5Me4Et)3Co3AsSe5][Cr(CO)5I]

The reaction of K3AsS3 with [Cp#Co(CO)I2] (Cp#=Cp* (C5Me5) or Cpx (C5Me4Et)) in DMF at 120°C gave violet [Cp#2Co2As2S3] 1#, dark brown [Cp#3Co3AsS6]I 2#, and dark brown [Cp#3Co3AsS5]I 3#. Whereas compounds 1# are already known, 2# and 3# were characterized by IR, 1H-NMR and mass spectra. A crystal structure determination of 3(Cp)x reveals a salt-like character with [Cpx3Co3AsS5]+ cations and iodide in a 1:1 ratio. In the cation the three Co atoms are connected by a μ3-S and a μ3-AsS4 ligand, thus forming a distorted Co3AsS4-cube. An additional sulfur atom is inserted into one of the As–S edges. The reaction of [Cp#2Co2I4] with K2As4Se6 in DMF at 120°C gave the brown salts [Cp#3Co3AsSe5]I 5#. For characterization, compound 5(Cpx) was reacted with [Cr(CO)5THF]. An X-ray diffraction analysis of the resulting [Cpx3Co3AsSe5][Cr(CO)5I] 8(Cpx) reveals a molecular structure similar to that of 3(Cp)x, but with a [Cr(CO)5I]− anion. In the cation all sulfur atoms are replaced by Se atoms.