A Mixed Arsenic-Phosphorus Centered Biradicaloid

Main‐group singlet biradicaloids have been thoroughly investigated in the past two decades, especially derivatives of cyclobutane‐1,3‐diyl. However, in each of the known examples, the radical centers are identical. Therefore, we sought to prepare a mixed dipnictadiazanediyls with P and As bearing the radical character. To achieve this goal, the unprecedented cyclodichloro arsaphosphadiazane [ClP(μ‐NTer)2AsCl] had to be prepared first. Treatment of [ClP(μ‐NTer)2AsCl] with a halide‐ing agent led to the novel cyclic cation [P(μ‐NTer)2AsCl]+, while reduction with magnesium afforded the first arsaphosphadiazanediyl [P(μ‐NTer)2As]. When you are two you cannot be too radical: The first biradicaloid with different radical centers, heteroatomic biradicaloid [P(μ‐NR)2As], was obtained by reducing the corresponding dichloroarsaphosphadiazane with magnesium. Structure elucidation revealed a kite‐shaped planar four‐membered N2PAs ring with two equal PN and AsN distances (see scheme, note in German the word for kite is Drachen, and dragon is Drache).