Abstract
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.