Synthesis, Structure, and Lewis Acidity of Heavy Pnictenium Cations

Strained pnictanes L 1 PnNaph (Pn = Sb 1 , Bi 2 ; L 1 = 2,6‐(2,4,6‐ i ‐Pr 3 C 6 H 2 ) 2 C 6 H 3 ) were synthesized and protonation reactions with [H(OEt 2 ) 2 ][BAr F ] (BAr F = B(3,5‐(CF 3 ) 2 C 6 H 3 ) 4 ) investigated. Et 2 O‐coordinated pnictenium cations [1‐L 1 Pn(OEt 2 )‐8‐ H ‐Naph][BAr F ] (Pn = Sb 3 , Bi 4 ) were formed in CH 2 Cl 2 (DCM) solution, whereas benzene‐coordinated cations [1‐L 1 Pn(C 6 H 6 )‐8‐ H ‐Naph][BAr F ] (Pn = Sb 5 , Bi 6 ) were isolated from solutions in benzene. The addition of acetonitrile (MeCN) to solutions of 3 – 6 yielded MeCN‐coordinated cations [1‐L 1 Pn(MeCN)‐8‐ H ‐Naph][BAr F ] (Pn = Sb 7 , Bi 8 ), whereas repeated recrystallization experiments of 5 and 6 from solutions in n ‐hexane finally gave “donor‐free” complexes [1‐L 1 Pn‐8‐ H ‐Naph][BAr F ] (Pn = Sb 9 , Bi 10 ), respectively. The compounds were characterized by heteronuclear NMR ( 1 H, 11 B, 13 C{ 1 H}, 19 F) and IR spectroscopy and single‐crystal X‐ray diffraction. Their electronic structures were analyzed by means of quantum chemical calculations, whereas the Lewis acidity of selected cations was evaluated by experimental and computational methods.