Synthesis and characterization of hexakis(acetonitrile)chromium(III) tetrafluoroborate, [CrIII(NCMe)6][BF4]3. A nonaqueous CrIII source☆ Original Research Article

Oxidation of [CrII(NCMe)4][BF4]2 with thianthrinium tetrafluoroborate forms [CrIII(NCMe)6][BF4]3 exhibiting two νCN absorptions at 2331 and 2301 cm−1, and has been structurally characterized with an average Cr–N distance of 1.999 Å. From the electronic absorption spectra the ligand field splitting, Δ0, is 20,160 cm−1, which is slightly larger than [CrIII(OH2)6]3+ in accord with the divalent chromium analogues. The 298 K ESR has a resonance at g=1.9884, and the magnetic susceptibility has a 300 K moment of 3.85μB characteristic of S=3/2 Cr(III). The field dependence of the magnetization can be fit to the Brillouin function also characteristic of S=3/2.