Coordination Chemistry of Polynitriles, I. Syntheses and Crystal Struc-

Dedicated to Professor Heinrich Nöth on the occasion of his 85th birthday Recrystallization of silver pentacyanocyclopentadienide Ag[C5(CN)5] from N,N-dimethylformamide (DMF) gives the polymeric 1 : 1 complex [Ag{C5(CN)5}(DMF)] (1). The Ag+ cation is coordinated by three N atoms of three different [C5(CN)5] anions and two O atoms of two DMF molecules. Each [C5(CN)5] is coordinated via three neighboring CN groups to three different Ag+ ions, while each DMF molecule bridges two Ag+ ions via its O atom. Treatment of NiCl2·6H2O, CoCl2·6H2O or ZnCl2 with Ag[C5(CN)5] in DMF gives the DMF complexes [M(DMF)6][C5(CN)5]2 (M = Ni, 2; Co, 3; Zn, 4). The complexes 2 and 3 were characterized by X-ray diffraction and show octahedral [M(DMF)6] cations with O-coordinated DMF molecules. The [C5(CN)5] anions show ideal pentagonal symmetry.