Cd(Sn9)2]6− and [Cd(Ni@Sn9)2]6−: Reactivity and coordination chemistry of empty and Ni-centered [Sn9]4− Zintl ions

Abstract

To investigate the reactivity of homoatomic clusters [E 9 ] 4− (E = Si-Pb) and intermetalloid clusters [M@E 9 ] q− , the reactions of the Zintl anions [Sn 9 ] 4− and [Ni@Sn 9 ] 4− with the CdMes 2 (Mes = Mesitylene) in the presence of 2.2.2-crypt were carried out. Two new compounds [K(2.2.2-crypt)] 6 [(Sn 9 )Cd(Sn 9 )]•en ( 1 ) and [K(2.2.2-crypt)] 6 [(Ni@Sn 9 )Cd(Ni@Sn 9 )]•en ( 2 ) were afforded. Both 1 and 2 were characterized by single-crystal X-ray diffraction, energy dispersive X-ray (EDX), and electrospray ionization mass spectrometry (ESI-MS), and can be viewed as two [Sn 9 ] 4− or [Ni@Sn 9 ] 4− subunits bridged by Cd ion in an η 3 : η 3 coordination mode. Quantum chemical calculations reveal the relationships between the geometries and electronic structures of clusters 2a , [Ni 3 Ge 18 ] 4− and [Cu 4 @Sn 18 ] 4− . Further electron localization technique (AdNDP method) was performed to explain chemical bonding patterns of 1a . The sandwich-like structure of [Sn 9 CdSn 9 ] 6− and [(Ni@Sn 9 )Cd(Ni@Sn 9 )] 6− and corresponding frontier molecular orbitals.