Synthesis\nand Characterization of a 1,2,4-Diazarsolide\nAnion

Cyclopentadienyl anions ([Cp]<sup>−</sup>) are\npervasive\nligands in coordination chemistry. In contrast, heavy-element derivatives\nof these ligands, particularly those that feature arsenic, are not\nas well developed. In this work, a new arsenic-based heterocycle with\na structure analogous to [Cp]<sup>−</sup> is presented. Reaction\nof K<sub>3</sub>As<sub>7</sub> with benzyl azide (BnN<sub>3</sub>)\nleads to fragmentation of the [As<sub>7</sub>]<sup>3–</sup> core and C–H activation of two [BnN] units to give the five-membered\narsenic heterocycle [As(NC(Ph))<sub>2</sub>]<sup>−</sup>. This\narsenic heterocycle was studied by nuclear magnetic resonance and\nUV–vis spectroscopy, X-ray diffraction, and its electronic\nstructure was investigated computationally.