Heavy Carbene Analogues: Donor-Free Bismuthenium and Stibenium Ions.

Kinetically stabilized congeners of carbenes, R2 C, possessing six valence electrons (four bonding electrons and two non-bonding electrons) have been restricted to Group 14 elements, R2 E (E=Si, Ge, Sn, Pb; R=alkyl or aryl) whereas isoelectronic Group 15 cations, divalent species of type [R2 E]+ (E=P, As, Sb, Bi; R=alkyl or aryl), were unknown. Herein, we report the first two examples, namely the bismuthenium ion [(2,6-Mes2 C6 H3 )2 Bi][BArF 4 ] (1; Mes=2,4,6-Me3 C6 H2 , ArF =3,5-(CF3 )2 C6 H3 ) and the stibenium ion [(2,6-Mes2 C6 H3 )2 Sb][B(C6 F5 )4 ] (2), which were obtained by using a combination of bulky meta-terphenyl substituents and weakly coordinating anions.