Synthesis, Structure and Reactivity of a Cyapho(dicyano)methanide Salt

We describe the synthesis of a cyapho(dicyano)methanide salt, [K(18‐crown‐6)][C(CN)(2)(CP)], from reaction of [Na(18‐crown‐6)][PH(2)] (18‐crown‐6=1,4,7,10,13,16‐hexaoxacyclooctadecane) with 1,1‐diethoxy‐2,2‐dicyanoethylene (EtO)(2)C=C(CN)(2). The reaction proceeds through a Michael addition‐elimination pathway to afford [Na(18‐crown‐6)][HP{C(OEt)=C(CN)(2)}]. Addition of a strong, non‐nucleophilic base (KHMDS) to this intermediate results in the formation of [K(18‐crown‐6)][C(CN)(2)(CP)]. Subsequent reactivity studies reveal that the cyapho(dicyano)methanide ion is susceptible to protonation with strong acids to afford the parent acid HC(CN)(2)(CP). The reactivity of the cyaphide moiety in [C(CN)(2)(CP)](−) was explored through coordination to metal centers and in cycloaddition reactions with azides.