Crystal structure of (1,4,7,10,13,16-hexaoxacyclooctadecane-κ 6O6)potassium(2-methylphenylamino)ethyl-2-methylphenylamide ammoniate (1/3.5), [K(18-crown-6)](o-CH3C6H4)NH(CH2)2N(o-CH3C6H4) 3.5 NH3, C28H53.5KN5.5O6

C28H53.5KN5.5O6, monoclinic, Pc (no. 7), a = 18.7986(12) Å, b = 8.3431(6) Å, c = 22.4638(16) Å, β = 100.554(5)°, V = 3463.6(4) Å3, Z = 4, Rgt (F) = 0.0712, wRref (F 2) = 0.2226, T = 150 K.

[Sn8 ]6- -Bridged Mixed-Valence ZnI /ZnII in {[K2 ZnSn8 (ZnMes)]2 }4- Inverse Sandwich-Type Cluster Supported by a ZnI -ZnI Bond

Since [Sn₈ ]^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 {[K₂ ZnSn₈ (ZnMes)]₂ }^4- (1 a), in which the highly charged [Sn₈ ]^6- is captured by mixed-valence Zn^I /Zn^II to form the dimer {closo-[Zn₂ Sn₈ ]}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 [Sn₈ ]^6- cluster can act as a novel bridging ligand, like arene, with a η⁴ :η⁴ -fashion. Theoretical calculations indicate that a significant delocalization of electrons over Zn atoms plays a vital role in the stabilization of the [Sn₈ ]^6- species. The AdNDP and magnetic response analyses clearly showed the presence of local σ-aromaticity in three cluster fragments: two ZnSn₄ caps and Sn₈ square antiprism.