*Article* **Coordination Chemistry of Polynitriles, Part XII— Serendipitous Synthesis of the Octacyanofulvalenediide Dianion and Study of Its Coordination Chemistry with K<sup>+</sup> and Ag<sup>+</sup>**

**Patrick Nimax, Yannick Kunzelmann and Karlheinz Sünkel \***

Department Chemistry, Ludwig-Maximilians University Munich, Butenandtstr. 5-13, 81377 Munich, Germany **\*** Correspondence: suenk@cup.uni-muenchen.de

**Abstract:** The reaction of diazotetracyanocyclopentadiene with copper powder in the presence of NEt4Cl yields, unexpectedly, besides the known NEt<sup>4</sup> [C5H(CN)<sup>4</sup> ] (3), the NEt<sup>4</sup> salt of octacyanofulvalenediide (NEt<sup>4</sup> )2 [C10(CN)<sup>8</sup> ] (**5**), which can be transformed via reaction with AgNO<sup>3</sup> to the corresponding Ag<sup>+</sup> salt (**4**), which in turn can be reacted with KCl to yield the corresponding K<sup>+</sup> salt **6**. The molecular and crystal structures of **4**–**6** could be determined, and show a significantly twisted aromatic dianion which uses all its nitrile groups for coordination to the metals; **4** and **6** form three-dimensional coordination polymers with fourfold coordinated Ag<sup>+</sup> and eightfold coordinated K + cations.

**Keywords:** diazotetracyanocyclopentadiene; octacyanofulvalenediide; radical chemistry; coordination polymers
