Sn/As-Based P4-Analogous Zintl Anions (Sn2As2)2– and (HSn3As)2–

Despite being composed of atoms of notably different atomic radii, the P4-analogous anion (Sn2As2)2– was obtained upon treatment of a ternary solid with the nominal composition ‘K2SnAs’ with ethane-1,2-diamine and crypt-222 by careful control of the reaction conditions and workup. X-ray diffraction and 119Sn NMR studies aided by sophisticated theoretical predictions showed that this anion co-crystallizes together with the protonated species (HSn3As)2–. The co-crystallization requires protonation of the latter to match the 2– charge of the other dianion in the salt. The studies also show that the P4-analogous anions are readily oxidized to give (Sn7As2)2–. In situ investigations using NMR revealed the co-existence of (Sn2As2)2– and (HSn3As)2– in solution. The study showcases the first binary P4-analogous Zintl anions comprising the elemental combination of Sn and As, which will be studied in terms of their reactivity toward d-block and f-block metal compounds in future work.