Synthesis and Characterization of the Chain Borosulfates (NH₄)₃[B(SO₄)₃] and Sr[B₂(SO₄)₄]

Abstract

Two new borosulfates were obtained either by an open vessel synthesis from sulfuric acid and B(OH) 3 , yielding (NH 4 ) 3 [B(SO 4 ) 3 ] or from solvothermal synthesis in oleum enriched sulfuric acid and B(OH) 3 , yielding Sr[B 2 (SO 4 ) 4 ]. (NH 4 ) 3 [B(SO 4 ) 3 ] crystallizes homeotypic to K 3 [B(SO 4 ) 3 ] in space group Ibca ( Z = 8, a = 728.58(3) pm, b = 1470.84(7) pm, c = 2270.52(11) pm), comprising open branched vierer single chains { 1 ∞ [B(SO 4 ) 2 (SO 4 ) 2/2 ] 3– }. Sr[B 2 (SO 4 ) 4 ] crystallizes as an ordered variant of Pb[B 2 (SO 4 ) 4 ] in space group Pnna ( Z = 4, a = 1257.4(4) pm, b = 1242.1(4) pm, c = 731.9(2) pm), consisting of loop branched vierer single chains { 1 ∞ [B(SO 4 ) 4/2 ] 2– }. Vibrational spectroscopy confirms both refined structure models. Thermal analysis of the dried powders, showed a decomposition towards the binary and ternary components, whereas a thermal treatment in the presence of the mother liquor promotes a decomposition of Sr[B 2 (SO 4 ) 4 ] towards Sr[B 2 O(SO 4 ) 3 ].