CpPEt2 As4 -An Organic-Substituted As4 Butterfly Compound.

CpPEt2 As4 (CpPEt =C5 (4-EtC6 H4 )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 CpPEt2 As4 , 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 CpBIG2 P4 (2; CpBIG =C5 (4-nBuC6 H4 )5 ). DFT calculations show the importance of dispersion forces for the stability of the products.