(C 2 H 10 N 2 )[BPO 4 F 2 ] — Structural Relations between [BPO 4 F 2 ] 2— and [Si 2 O 6 ] 4—

(C 2 H 10 N 2 )[BPO 4 F 2 ] — Strukturbeziehungen zwischen [BPO 4 F 2 ] 2— und [Si 2 O 6 ] 4— Colourless crystals of (C 2 H 10 N 2 )[BPO 4 F 2 ] were prepared from mixture of ethylendiamine, H 3 BO 3 , BF 3 · C 2 H 5 NH 2 , H 3 PO 4 and HCl under mild hydrothermal conditions (220 °C). The crystal structure was determined by single crystal methods (triclinic, P 1¯ (no. 2), a = 451.85(5) pm, b = 710.20(8) pm, c = 1210.2(2) pm, α = 86.08(1)°, β = 88.52(2)°, γ = 71.74(1)°, Z = 2) and contains infinite tetrahedral zweier‐single‐chains   ∞ 1 {[BPO 4 F 2 ] 2— } which are isoelectronic (48e — ) with the polyanions   ∞ 1 {[Si 2 O 6 ] 4— } of the pyroxene family.