Systematic DFT Studies on Binary Pseudo-Tetrahedral Zintl Anions: Relative Stabilities and Reactivities Towards Protons, Trimethylsilyl Groups, and Iron Complex Fragments.

Binary pseudo -tetrahedral Zintl anions composed of (semi-)metal atoms of the p-block elements have proven to be excellent starting materials for the synthesis of a variety of heterometallic and intermetalloid transition metal-main group metal cluster anions. However, only 11 of the theoretically possible 48 anions have been experimentally accessed to date as isolable salts. This brings up the question, whether the other species are generally not achievable, or whether synthetic chemists just did not succeed in their preparation so far. To contribute to a possible answer to this question, we calculated global minimum structures for all anions of the type (TrTt 3 ) 5 - , (TrPn 3 ) 2- , and (Tt 2 Pn 2 ) 2- , comprising elements of periods 3 to 6 (Tr: triel, Al···Tl; Tt: tetrel, Si···Pb; Pn: pnictogen, P···Bi). By analyzing the computational results, we developed a concept to predict which of the yet missing anions should be synthesizable and why. Additionally, we describe molecular structures that would result upon electrophilic attack by protons or trimethylsilyl groups, or upon nucleophilic attack by transition metal complex fragments. The latter yields butterfly-like structures that can be viewed as a new form of adaptable tridentate chelating ligands.