Synthesis, Structure and Chemical Bonding of Polyantimony Clusters Containing Coinage Metals [M₂Sb₁₄]^4- (M = Cu, Ag)

Binary polyantimony clusters, namely [Cu2Sb14](4-) and [Ag2Sb14](4-), containing coinage metals, were successfully synthesized and characterized, in which two homoatomic Sb-7(3-) subunits are bridged by two coinage metals in eta(4):eta(1) and eta(1):eta(1) coordination modes, respectively. In [Cu2Sb14](4-), two bridging Cu ions and two Sb atoms form a planar rhombic unit, which was revealed to have antiaromatic properties by theoretical calculations. Further electron structure and bonding analysis confirmed the presence of delocalized bonds in the rhombic unit and the metallophilic interaction between two formal M+ ions.