We report the observation of dimerization of two 8electron superatom cluster units in the crystallographic structures of Au 2 Ag 42 (SAdm) 27 (BPh 4 )a nd [Au 2 Ag 48 (S-t Bu) 20 -(Dppm) 6 Br 11 ]Br(BPh 4 ) 2 nanoclusters.T he crystallographic analysis reveals that both nanoclusters have aA u 2 Ag 24 core made of two separated icosahedral without sharing metal atoms,and each icosahedron has an eight-electron (8e) closed shell (1S 2 1P 6 ). The valence electronic structures of these two nanoclusters are analogous to that of aN ea tom dimer (Ne 2 ) according to the density functional theory (DFT) analysis.This is the first crystallographic observation of the dimerization of 8-electron superatom units.This study enriches the fundamental knowledge on metal superatom clusters and implies the possibility for further assembling metal superatom building blocks into higher order superatom molecules.Metal clusters,w hich can be bare (in molecular beams) or ligated (in solid-state or solution phase), have attracted wide research interest. [1][2][3][4][5][6] Clusters such as sodium (Na n ), [7,8] aluminum (Al n ), [9][10][11] gold (Au n ), [12,13] and alloy clusters, [14,15] with certain numbers of atoms have been discovered to exhibit pronounced intensities in their mass spectra. Among these,t he "magic-sized" clusters with analogous valence electron configuration to atomic electron structure are regarded as superatoms,and ac losed-shell electronic configuration for such clusters in as phere model has been developed for understanding their extraordinary stability. [16][17][18] Further,several experimental and theoretical studies present that the superatom clusters can serve as the building block to form assemblies or compounds in combination with other atoms or superatom. [19][20][21][22][23] Ther esearch on the superatom-superatom interactions provide nanomaterials with new structure,s uperior bonding models,a nd various properties, promote the development of chemistry and materials science. [19][20][21][22][23][24][25] Thel igand-protected gold clusters having closed electronic shells are considered as superatoms owing to their noble-gas-atom-like valence electron configurations. [1] Several prototype gold superatom clusters,s uch as [Au 13 -(PMe 2 Ph) 10 Cl 2 ] 3+ (8e), [26] Au 39 (PR 3 ) 14 Cl 6 À (34e), [27] Au 25 -(SR) 18 À (8e) [28,29] and Au 102 (p-MBA) 44 (58e) [30] have been reported. Among nanoclusters,t he icosahedral metal cores which contain 8f ree valence electrons have been widely found in many gold/silver or doped superatom clusters such as [Au 13 (PMe 2 Ph) 10 Cl 2 ] 3+ , [26] MAu 24 (SR) 18 (M = Au/Pt/ Pd), [28,29,[31][32][33][34] MAg 24 (SR) 18 (M = Au/Ag/Pt/Pd), [35][36][37] [M 1 Ag 20 {S 2 P(OiPr) 2 } 12 ] + /[M 1 Ag 20 {Se 2 P(OEt) 2 } 12 ] + (M = Ag/ Au), [38,39] [M 1 Ag 19 {S 2 P(OR) 2 } 12 ]( M = Ag/Au), [40,41] [M 1 Ag 16 -(SR) 12 ] 3À . [42,43] In all known superatom and supermolecule clusters,t he 8e icosahedral superatom units typically share at least one metal atom when they form assembled str...