Pd(2)@Sn(18)(4-): fusion of two endohedral stannaspherenes.

Stannaspherene refers to an icosahedral 12-atom Sn cage cluster (Sn122-) and has also been found to be able to trap all transition metals to form gaseous endohedral clusters (M@Sn12-). During exploratory solution syntheses of endohedral stannaspherenes, a new closo-deltahedral cluster, Pd2@Sn184-, 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 Pd2@Sn184- cluster has pseudo-D3d symmetry and is composed of 18 Sn atoms encapsulating two Pd atoms. It can be viewed as the fusion of two endohedral stannaspherenes (Pd@Sn122-) along their C3 axis by removing a Sn3 triangle on each Sn12 unit at the cluster−cluster interface. Electronic structure calculations show that Pd2@Sn184- consists of a Sn184- cage with two zero-valent Pd atoms and possesses a highly stable electronic configuration.