Synthesis and characterization of hexakis(acetonitrile)chromium(III) tetrafluoroborate, [Cr III(NCMe) 6][BF 4] 3. A nonaqueous Cr III source ☆

Abstract

Oxidation of [Cr II(NCMe) 4][BF 4] 2 with thianthrinium tetrafluoroborate forms [Cr III(NCMe) 6][BF 4] 3 exhibiting two ν C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, Δ 0, is 20,160 cm −1, which is slightly larger than [Cr III(OH 2) 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 3.85 μ B 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.