Highly Soluble Supertetrahedra upon Selective Partial Butylation of Chalcogenido Metalate Clusters in Ionic Liquids

Supertetrahedral clusters have been reported in two generally different types so far: one type possessing an organic ligand shell, no or low charges, and high solubility, while the other cluster type is ligand‐free with usually high charges and low or no solubility in common solvents. The latter is a tremendous disadvantage regarding further use of the clusters in solution. However, as organic substituents usually broaden the HOMO–LUMO gaps, which cannot be overcompensated by the (limited) cluster sizes, a full organic shielding comes along with drawbacks regarding opto‐electronic properties. We therefore sought to find a way of generating soluble clusters with a minimum number of organic substituents. Here, we present the synthesis and full characterization of two salts of [Sn10O4S16(SBu)4]4− that are high soluble in CH2Cl2 or CH3CN, which includes first NMR and mass spectra obtained from solutions of such salts with mostly inorganic supertetrahedral clusters. The optical absorption properties of this new class of compounds indicates nearly unaffected band gaps. The synthetic approach and the spectroscopic findings were rationalized and explained by means of high‐level quantum chemical studies.
Selective access to partially butylated supertetrahedral clusters [Sn10O4S16(SBu)4]4− was achieved by employing a di‐butylated ionic liquid as reaction medium and alkylation agent. In contrast to purely inorganic [Sn10O4S20]8−, the butylated analogs are soluble in solvents like CH2Cl2 or CH3CN, without losing the typical opto‐electronic properties. Solution‐NMR data were assigned with the help of newly developed all‐electron relativistic DFT methods.