Fluorination of closo , closo ‐[B 21 H 18 ] – with a HF and F 2 to yield closo , closo ‐[B 21 H 18– x F x ] – ( x = 1–3) and closo , closo ‐[B 21 F 18 ] –

[B 21 H 18 ] – reacts with anhydrous HF at 100 °C, depending on the reaction time, to various compounds with the form[7‐F‐B 21 H 17 ] – , [7, 8′‐F 2 ‐B 21 H 16 ] – , [7, 8‐F 2 ‐B 21 H 16 ] – , [7, 8, 9′‐F 3 ‐B 21 H 15 ] – and [7, 8, 9‐F 3 ‐B 21 H 15 ] – . [B 21 F 18 ] – is available by the reaction of [B 21 H 18 ] – with F 2 in a HF. The mentioned borates were characterized by NMR spectroscopy. Crystal structures of salts with [B 21 H 18– x F x ] – ( x = 1–3) were determined.