2D‐Polymeric Anion Networks: The Two Novel Perselenoborates BaB2Se6 and Ba2B4Se13

Systematic investigations of ternary barium selenoborates led to the new compounds BaB₂Se₆ and Ba₂B₄Se₁₃ which represent the first alkaline earth perselenoborates. Appropriate amounts of barium selenide, boron and selenium were filled into carbon coated silica tubes which were sealed under vacuum. The high temperature reactions and subsequent annealing processes were performed in horizontal one‐zone furnaces. By means of single crystal X‐ray diffraction the structure of BaB₂Se₆ was determined to be orthorhombic, space group Cmca (no. 64) with a = 11.326(2)Å, b = 7.659(2)Å and c = 10.315(2)Å, while for Ba₂B₄Se₁₃ the monoclinic space group P2₁/c (no. 14) was found with a = 12.790(3)Å, b = 11.560(2)Å, c = 12.862(3)Å and β = 103.22(3)°. BaB₂Se₆ exhibits infinite layers of B₂Se₆^2—]_∞‐anions oriented parallel to the a‐b‐plane. Each layer consists of B₂Se₂four‐membered rings, which are connected via four diselenide bridges. Thus, B₆Se₁₂‐rings are formed in which the barium cations are located. Likewise, in Ba₂B₄Se₁₃ polymeric B₄Se₁₃^4—]_∞‐anions are running parallel to the a‐c‐plane resulting in a new layered structure type built of alternating B₂Se₄‐ and B₂Se₃‐rings which are connected by perseleno contacts.