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.