Abstract
Cyclopentadienyl anions ([Cp](-)) are pervasive ligands in coordination chemistry. In contrast, heavy-element derivatives of these ligands, particularly those that feature arsenic, are not as well developed. In this work, a new arsenic-based heterocycle with a structure analogous to [Cp](-) is presented. Reaction of K(3)As(7) with benzyl azide (BnN(3)) leads to fragmentation of the [As(7)](3-) core and C-H activation of two [BnN] units to give the five-membered arsenic heterocycle [As(NC(Ph))(2)](-). This arsenic heterocycle was studied by nuclear magnetic resonance and UV-vis spectroscopy, X-ray diffraction, and its electronic structure was investigated computationally.