Synthesis and Characterization of the Nitrosonium Borosulfates (NO)[B(SO4)2] and (NO)[B(S2O7)2]

The solvothermal reaction of boron oxide and oleum (65% SO3) in the presence of nitrosonium cations resulted in the formation of the first nitrosonium borosulfates. By careful adjustment of the initial boron content as well as the reaction temperature, we achieved the selective synthesis of two distinct borosulfates featuring S–O–S and B–O–S bridges, respectively. (NO)[B(S2O7)2] crystallizes homeotypically to A[B(S2O7)2] (A = NH4, K) in space group Cc (no. 9, Z = 8, a = 11.3824(6) Å, b = 14.6067(7) Å, c = 13.6858(6) Å, β = 95.128(2)°) and contains molecular [B(S2O7)2]− anions. In addition, one-dimensional, SiS2-analogue chains are present in (NO)[B(SO4)2], which crystallizes in space group Pccn (no. 56, Z = 4, a = 9.0046(2) Å, b = 9.0780(3) Å, c = 7.4462(2) Å) homeotypically to A[B(SO4)2] (A = NH4, K). Vibrational spectroscopy confirms both structural models, including the presence of S–O–S bridges. Thermal analysis revealed the transformation of S–O–S bridges in (NO)[B(S2O7)2] to B–O–S bridges in (NO)[B(SO4)2]. The charge-to-radius ratio of the cation was identified as structure-directing parameter for [B(SO4)2] chains.