From Neutral Diarsenes to Diarsene Radical Ions and Diarsene Dications.

Diarsene [L(MeO)GaAs] 2 (L=HC[C(Me)N(Ar)] 2 , Ar=2,6- i Pr 2 C 6 H 3 , 4) reacts with MeOTf and Me NHC ( Me NHC=1,3,4,5-tetra-methylimidazol-2-ylidene) to the diarsene [L(TfO)GaAs] 2 (5) and the carbene-coordinated diarsene [L(MeO)GaAsAs( Me NHC)Ga(OMe)L] (6). The NHC-coordination results in an inversion of the redox properties of the diarsene 4, which shows only a reversible reduction event at E 1/2 =-2.06 V vs Fc 0/+1 , whereas the carbene-coordinated diarsene 6 shows a reversible oxidation event at E 1/2 =-1.31 V vs Fc 0/+1 . Single electron transfer reactions of 4 and 6 yielded [K[2.2.2.]cryp][L(MeO)GaAs] 2 (8) and [L(MeO)GaAsAs( Me NHC)-Ga(OMe)L][B(C 6 F 5 ) 4 ] (9) containing the radical anion [L(MeO)GaAs] 2 ⋅ - (8⋅ - ) and the NHC-coordinated radical cation [L(MeO)GaAsAs( Me NHC)Ga(OMe)L]⋅ + (9⋅ + ), respectively, while the salt-elimination reaction of the triflate-coordinated diarsene 5 with Na[B(C 6 F 5 ) 4 ] gave [LGaAs] 2 [B(C 6 F 5 ) 4 ] 2 (11) containing the dication [LGaAs] 2 2+ (11 2+ ). Compounds 1-11 were characterized by 1 H and 13 C NMR, EPR (8, 9), IR, and UV-Vis spectroscopy and by single crystal X-ray diffraction (sc-XRD). DFT calculations provided a detailed understanding of the electronic nature of the diarsenes (4, 6) and the radical ions (8⋅ - , 9⋅ + ), respectively.