Pd2@Sn184-:: Fusion of two endohedral stannaspherenes

Stannaspherene refers to an icosahedral 12-atom Sn cage cluster (Sn-12(2-)) and has also been found to be able to trap all transition metals to form gaseous endohedral clusters (M@Sn-12(-)). During exploratory solution syntheses of endohedral stannaspherenes, a new closo-deltahedral cluster, Pd-2@Sn-18(4-), has been isolated as a (2,2,2-crypt)K+ salt through the reaction of K4Sn9 and Pd[P(C6H5)(3)](4) in ethylenediamine solutions and characterized via X-ray crystallography. The new Pd-2@Sn-18(4-) cluster has pseudo-D-3d symmetry and is composed of 18 Sn atoms encapsulating two Pd atoms. It can be viewed as the fusion of two endohedral stannaspherenes (Pd@Sn-12(2-)) along their C-3 axis by removing a Sn-3 triangle on each Sn-12 unit at the cluster-cluster interface. Electronic structure calculations show that Pd-2@Sn-18(4-) consists of a Sn-18(4-) cage with two zero-valent Pd atoms and possesses a highly stable electronic configuration.