CpPEt2As4-An Organic-Substituted As4 Butterfly Compound

CpPEt2As4 (CpPEt=C5(4‐EtC6H4)5) (1) is synthesized by the reaction of CpPEt. radicals with yellow arsenic (As4). In solution an equilibrium of the starting materials and the product is found. However, 1 can be isolated and stored in the solid state without decomposition. As4 can be easily released from 1 under thermal or photochemical conditions. From powder samples of CpPEt2As4, yellow arsenic can be sublimed under rather mild conditions (T=125 °C). A similar behavior for the P4‐releasing agent was determined for the related phosphorus compound CpBIG2P4 (2; CpBIG=C5(4‐nBuC6H4)5). DFT calculations show the importance of dispersion forces for the stability of the products. As you like it: As4 butterfly compounds are rare and even unknown with organic substituents. The first organo‐derivative CpPEt2As4 (see structure; CpPEt=C5(4‐EtC6H4)5) is prepared and the liberation of yellow arsenic from it is demonstrated in solution and in the solid state. Similar results were found for the related P4 butterfly molecule CpBIG2P4 (CpBIG=C5(4‐nBuC6H4)5).