Two synthetic approaches for the preparation of tin(ii) dications

Abstract

Examples of tin dications without closer contacts to the anion are rare, as are straightforward routes to weakly coordinated tin(II) dication salts. Here we report on the synthesis of [Sn(MeCN)₆][Al(OR^F)₄]₂ (R^F = C(CF₃)₃) via NO⁺-oxidation of tin metal. Subsequently, [Sn(MeCN)₆][Al(OR^F)₄]₂ was used to prepare the mixed coordinated [Sn(pyr)₂(MeCN)₄][Al(OR^F)₄]₂ and [Sn(PPh₃)₂-(MeCN)₅][Al(OR^F)₄]₂·MeCN. Additionally, [Sn(dmap)₄][Al(OR^F)₄]₂ was prepared via a reaction of dmap with [SnCp][Al(OR^F)₄]. The generality of the formation of tin(II) dications by reacting [SnCp]⁺ and L to give [SnL_x]²⁺ and SnCp₂ was investigated using DFT calculations. Extensions to [ECp*]⁺ cations (E = Si, Ge, Sn, and Pb) are also suggested to be useful for the preparation of E(II) dications.