Sr[B₂(SO₄)₃(S₂O₇)]: A Borosulfate with an Unprecedented Chain Structure Comprising Disulfate Groups

Abstract

Unconventional borosulfates containing S–O–S bridges are still rare. Sr­[B2(SO4)3(S2O7)] was synthesized solvothermally in oleum (65% SO3) and crystallizes in a new structure type in space group P21/n (Z = 4, a = 747.0(2) pm, b = 1533.4(4) pm, c = 1222.0(3) pm, β = 93.293(10)°). The structure features loop-branched vierer double chains, in which two terminal sulfate tetrahedra are condensed to a disulfate group. The resulting ratio between boron and sulfur of 2:5 was not yet found in borosulfate chemistry. The presence of S–O–S bridges was confirmed by FT-IR spectroscopy. Temperature-programmed X-ray powder diffraction in addition to thermogravimetric analysis revealed a transformation from chains containing S–O–S bridges in Sr­[B2(SO4)3(S2O7)] to chains containing solely B–O–S bridges in Sr­[B2(SO4)4] and to chains containing B–O–B bridges in Sr­[B2O­(SO4)3].

Triple‐Vertex Linkage of (BO4)‐Tetrahedra in a Borosulfate: Synthesis, Crystal Structure, and Quantum‐Chemical Investigation of Sr[B3O(SO4)4(SO4H)]

“…The anionic substructures of borosulfates are similar to silicates, exhibiting soro‐, neso‐, cyclo ‐, ino ‐, phyllo ‐, and tectosilicates like topologies of vertex connected (BO 4 )‐ and (SO 4 )‐tetrahedra. [3] Even the formation of S‐O‐S[ 3b , 3c , 3e , 4 , 5 ] and B‐O‐B[ 3i , 6 , 7 , 8 , 9 ] bonds is not uncommon. This finding is in contrast to the structures of alumosilicates, wherein Al‐O‐Al bonds are not to be expected according to Loewenstein's rule.…”

Ag[B(S2O7)2]: The First Transition Metal Borosulfate Featuring Disulfate Groups

“…Unlike the decompositions of the divalent metal borosulfates Ba[B(S 2 O 7 ) 2 ] 2 and Sr[B 2 (SO 4 ) 3 (S 2 O 7 )], [19,20] no further transformation from B−O−S bridges towards B−O−B bridges was observed. Similarly, for the monovalent metal and non‐metal borosulfates A [B(S 2 O 7 ) 2 ] ( A =Li−K, NH 4 ) also only a transformation from S−O−S bridges to B−O−S bridges was reported, so that the corresponding borosulfates with B−O−B bridges remained unknown so far [21,22] .…”

“…In case of main group metal borosulfates, compounds featuring S−O−S bridges typically decompose towards further borosulfates featuring solely B−O−S bridges [19–21] . Consequently, we investigated the thermal behavior of Ag[B(S 2 O 7 ) 2 ] as an example of the first transition metal borosulfate with disulfate groups.…”

“…Recently, we were able to achieve great progress in selective syntheses of borosulfates with respect to their connection pattern [19,20] . Thus, we could report on the first quaternary systems M O−B 2 O 3 −SO 3 ( M =Sr, Ba), where each connection pattern – S−O−S, B−O−S and B−O−B bridges ..– could be synthesized carefully controlling the oleum concentration during the synthesis.…”

Polymorphism and optical, magnetic and thermal properties of the either phyllo- or inosilicate-analogous borosulfate Cu[B2(SO4)4]

“…1,3–7 With the first crystalline borosulfate K 5 [B(SO 4 ) 4 ] discovered as recent as 2012, 8 there are over seventy compounds characterised to date. 7,9–15 Borosulfates may be classified as silicate-analogous 16 in two ways: on the one hand, their anions consist most commonly 15 of corner sharing borate and sulfate tetrahedra, solely. On the other hand, such structures can be understood by considering supertetrahedra TX 4 formed by a boron atom acting as centre T coordinated tetrahedrally by four SO 4 moieties X as frequently observed in the building unit [B(SO 4 ) 4 ] 5− .…”