Anionic Chains of Parent Pnictogenylboranes

We report on the synthesis and structural characterization of unprecedented anionic parent compounds of mixed Group 13/15 elements. The reactions of the pnictogenylboranes H₂E‐BH₂?NMe₃ ( 1 a =P, 1 b =As) with phosphorus and arsenic centered nucleophiles of the type [EH₂]^? (E=P, As) lead to the formation of compounds of the type [H₂E‐BH₂‐E′H₂]^? ( 2 : E=E′=P; 3 : E=E′=As; 4 : E=P, E′=As) containing anionic pnictogen–boron chain‐like units. Furthermore, a longer 5‐membered chain species [H₂As‐BH₂‐PH₂‐BH₂‐AsH₂]^? ( 5 ) and a cyclic compound [NHC^dipp‐H₂B‐PH₂‐BH₂‐NHC^dipp]⁺[P₅B₅H₁₉]^? ( 6 ) containing a n‐butylcyclohexane‐like anion were obtained. All the compounds have been characterized by X‐ray structure analysis, multinuclear NMR spectroscopy, IR spectroscopy, and mass spectrometry. DFT calculations elucidate their high thermodynamic stability, the charge distribution, and give insight into the reaction pathway.