A Step in Between: [Sn3Bi3](5-) and Its Structural Relationship to [Sn3Bi5](3-) and [Sn4Bi4](4.).

Extraction of "RbSnBi" in liquid ammonia yielded the cluster anion [Sn3Bi5](3-), which could be crystallized in the compound [Rb@[2.2.2]crypt]3[Sn3Bi5]⋅8.87 NH3. This anion is found to be derived from the formerly reported [Sn4Bi4](4-) by the formal substitution of one tin atom by bismuth. In contrast, the extraction of "RbSn2/Rb3Bi2" in liquid ammonia yielded the anion [Sn3Bi3](5-) in the compound Rb6[Sn3Bi3][Sn4]1/4⋅6.75 NH3. The structural correlation of the two novel clusters indicates that [Sn3Bi3](5-) might be an intermediate of the reaction pathway to [Sn3Bi5](3-) and [Sn4Bi4](4-). Each cluster is investigated by means of the electron localization function and further characterization was performed by using ESI-MS.