Simple Route to [PSH][B 9 H 14 ] and a Contemporary Study of Its Solid-State Dynamic Behavior.

The 1,8-bis(dimethylamino)naphthalenium ([PSH] + ) decaborane salt, [PSH][B 10 H 13 ], has been found to react in ethanol to form [PSH][B 9 H 14 ] ( 1 ), affording a simple route to the synthesis of the arachno -nonaborate anion. This new polyhedral salt is characterized by NMR spectroscopy and X-ray diffraction. The measurement of diffusion coefficients by NMR methods demonstrates that the [PSH] + cation and the [B 9 H 14 ] - anion form ion pairs in a non-coordinating solvent such as CH 2 Cl 2 , whereas in CD 3 CN the formation of ion pairs was not observed. Insights into the long-known low-energy dynamic behavior, which involves the bridging and endo -terminal hydrogen atoms, are elucidated using DFT calculations. Salts [PSH][B 9 H 14 ] ( 1 ) and [PSH][B 9 H 14 ]·0.5CHCl 3 (solvated, 1· 0.5CHCl 3 ) have also been studied by X-ray diffraction analysis. A solid-state NMR study has demonstrated that K[B 9 H 14 ] and [PSH][B 9 H 14 ] ( 1 ) undergo significantly different motion regimes, being a low-energy, weakly temperature-dependent process for 1 , which may be ascribed to some type of low-amplitude reorientation of the whole boron cages. This process may be the mechanism for the low- to-room-temperature order-disorder hidden transition found by X-ray analysis.