Crystalline Divinyldiarsene Radical Cations and Dications

Abstract

The divinyldiarsene radical cations [{(NHC)C(Ph)}As] 2 (GaCl 4 ) (NHC=IPr: C{(NDipp)CH} 2 3 ; SIPr: C{(NDipp)CH 2 } 2 4 ; Dipp=2,6‐ i Pr 2 C 6 H 3 ) and dications [{(NHC)C(Ph)}As] 2 (GaCl 4 ) 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 GaCl 3 . 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 π‐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 75 As ( I =3/2) nuclei.