Ammonium, Phosphonium, Arsonium, and Stibonium Ions

Superacidic protonation of MePF2 was also used to prepare the salts MePF2H+MF6 (M = As, Sb).556 The cations show distorted tetrahedral structure and weak P—F interionic contacts. 

Hydroxy(alkoxy)phosphonium Ions. Olah and McFarland560 studied the protonation in HS03F or HS03F-SbF5 solution of varied phosphorus oxyacids and derivatives. Treatment of tetravalent phosphoms compounds (phosphorus, phosphonic, and phosphinic acid and their trialkyl and triaryl derivatives) results in (9-protonation and the formation of hydroxyphosphonium ions. Trivalent phosphites, in turn, are protonated at the phosphorus atom. The 31P shifts observed for the latter ions are significantly deshielded, which was attributed to significant oxonium ion character. 

Minkwitz and Schneider561 obtained tetrahydroxyphosphonium salts by protonation of phosphorus acid with HF-AsF5 and HF-SbF5 [Eq. (4.155)]. XRD structure study shows that the cation of the hexafluoroantimonate salt has almost S4 symmetry and equal P—O bonds (1.529-1.536 A). Cations and anions in the crystals are linked three-dimensionally by hydrogen bonds (each cation is bonded to six anions). 

Laali et al. have studied the protonation of tetra-terf-butyltetraphosphacubane (227a) and tetra-tert-butyltetraarsacubane (227b). In the case of tetra-ferf-butyl- 

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