Metal-Centered Zintl Ions Isolated By Direct Extraction From Endohedral Intermetallic Precursor: [Co1-X@Sn-9](4-) (X Approximate To 0.32) And [Co-2@Sn-17](5-)

Two new compounds with Co-centered Sn-9 clusters were obtained by the extraction directly from the intermetallic precursor K4.79Co0.79Sn9 in ethylenediamine with addition of cryptand [2.2.2]. The anions [Co-0.68@Sn-9](4-) in K[K([2.2.2]crypt)](3)[Co-0.68@Sn-9] (1) consisting of overlaying [Co@Sn-9](4-) and [Sn-9](4-) cluster anions are connected by K atoms to form infinite K-1(infinity)[Co-0.68@Sn-9] chains. The anions [Co-2@Sn-17](5-) in [K([2.2.2]crypt)](5)[Co-2@Sn-17]entol (2) are built from two [Co@Sn-9] sharing one common Sn atom, with the same composition but a different conformation as in the previously reported [K([2.2.2]crypt)](5)[Co-2@Sn-17]. Quantum chemical calculations for the different conformers of [Co-2@Sn-17](5-) reveal that both conformers are rather close in energy and that the short intercluster Sn-Sn distance in 2 does not originate from attractive interactions.