Reactions of [Et<sub>4</sub>N]<sub>3</sub>[Bi{Fe(CO)<sub>4</sub>}<sub>4</sub>] with Alkyl Halides or Dihalides: A General Method for the Synthesis of Anionic Complexes of the Type [Et<sub>4</sub>N]<sub>2</sub>[RBi{Fe(CO)<sub>4</sub>}<sub>3</sub>] and the Cyclic Complexes R<sub>2</sub>Bi<sub>2</sub>Fe<sub>2</sub>(CO)<sub>8</sub> – 指紋