Synthesis and characterization of hexakis(acetonitrile)chromium(III) tetrafluoroborate, [Cr-III(NCMe)(6)][BF4](3). A nonaqueous Cr-III source

Oxidation of [Cr-II(NCMe)(4)][BF4](2) with thianthrinium tetrafluoroborate forms [Cr-III(NCMe)(6)][BF4](3) exhibiting two nu(Cequivalent toN) absorptions at 2331 and 2301 cm(-1), and has been structurally characterized with an average Cr-N distance of 1.999 Angstrom. From the electronic absorption spectra the ligand field splitting, Delta(0), is 20,160 cm(-1), which is slightly larger than [Cr-III(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 3.85mu(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. (C) 2003 Elsevier Ltd. All rights reserved.