[Sn<sub>8</sub>]<sup>6−</sup>‐Bridged Mixed‐Valence Zn<sup>I</sup>/Zn<sup>II</sup>in {[K<sub>2</sub>ZnSn<sub>8</sub>(ZnMes)]<sub>2</sub>}<sup>4−</sup>Inverse Sandwich‐Type Cluster Supported by a Zn<sup>I</sup>−Zn<sup>I</sup>Bond
Hong‐Lei Xu, Nikolay V. Tkachenko, Alvaro Muñoz‐Castro, Alexander I. Boldyrev, Zhong‐Ming Sun
Abstract
Abstract Since [Sn 8 ] 6− was discovered from the solid‐state phase in 2000, its solution chemistry has been elusive due to the high charges and chemical activity. Herein, we report the synthesis and characterization of an inverse sandwich‐type cluster dimer {[K 2 ZnSn 8 (ZnMes)] 2 } 4− ( 1 a ), in which the highly charged [Sn 8 ] 6− is captured by mixed‐valence Zn I /Zn II to form the dimer { closo ‐[Zn 2 Sn 8 ]} 2 moieties bridged by a Zn‐Zn bond. Such Zn‐Sn cluster not only exhibits a novel example of mixed‐valence Zn I /Zn II for stabilizing highly active anion species, but also indicates the [Sn 8 ] 6− cluster can act as a novel bridging ligand, like arene, with a η 4 :η 4 ‐fashion. Theoretical calculations indicate that a significant delocalization of electrons over Zn atoms plays a vital role in the stabilization of the [Sn 8 ] 6− species. The AdNDP and magnetic response analyses clearly showed the presence of local σ‐aromaticity in three cluster fragments: two ZnSn 4 caps and Sn 8 square antiprism.