Crystalline Divinyldiarsene Radical Cations and Dications

The divinyldiarsene radical cations [{(NHC)C(Ph)}As](2)(GaCl4) (NHC=IPr: C{(NDipp)CH}(2) 3; SIPr: C{(NDipp)CH2}(2) 4; Dipp=2,6-iPr(2)C(6)H(3)) and dications [{(NHC)C(Ph)}As](2)(GaCl4)(2) (NHC=IPr 5; SIPr 6) are readily accessible as crystalline solids on sequential one-electron oxidation of the corresponding divinyldiarsenes [{(NHC)C(Ph)}As](2) (NHC=IPr 1; SIPr 2) with GaCl3. Compounds 3-6 have been characterized by X-ray diffraction, cyclic voltammetry, EPR/NMR spectroscopy, and UV/vis absorption spectroscopy as well as DFT calculations. The sequential removal of one electron from the HOMO, that is mainly the As-As pi-bond, of 1 and 2 leads to successive elongation of the As=As bond and contraction of the C-As bonds from 1/2 -> 3/4 -> 5/6. The UV/vis spectrum of 3 and 4 each exhibits a strong absorption in the visible region associated with SOMO-related transitions. The EPR spectrum of 3 and 4 each shows a broadened septet owing to coupling of the unpaired electron with two As-75 (I=3/2) nuclei.