Progress in Polyarsolyl Chemistry

The synthesis of heteroatom analogues of the cyclopentadienyl anion Cp(−) is a fascinating and challenging field of research. The replacement of methine moieties by phosphorus is well investigated for the synthesis of mono‐, tri‐ and pentaphospholyl ligands. On the other hand, arsenic derivatives are rare and 1,2,4‐triarsolyl and tetraarsolyl salts are unknown. Herein, we report on the synthesis of Cs[E(3)C(2)(trip)(2)] (1 a: E=P; 1 b: E=As; trip=2,4,6‐triisopropylphenyl) and Cs[E(4)C(trip)] (2 a: E=P; 2 b: E=As). Compound 1 b represents the first 1,2,4‐triarsolyl and 2 b the first tetraarsolyl anion. All salts are obtained in one‐pot syntheses using E(SiMe(3))(3), 2,4,6‐triisopropylbenzoyl chloride and CsF. The products 1 a⋅2 C(4)H(8)O(2), 2 a⋅Et(2)O and 2 b⋅3 C(4)H(8)O(2) were characterized by X‐ray structural analysis, which revealed planar heterocycles. Nucleus‐independent chemical shifts (NICS) confirmed the aromaticity of these anions. Notably, compound 2 a⋅Et(2)O is only the second tetraphospholyl ligand which is structurally characterized.