Simple Route to [PSH][B9H14] and a Contemporary Study of Its Solid-State Dynamic Behavior

The 1,8-bis(dimethylamino)naphthalenium ([PSH](+)) decaborane salt, [PSH][B10H13], has been found to react in ethanol to form [PSH][B9H14] (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 [B9H14](-) anion form ion pairs in a non-coordinating solvent such as CH2Cl2, whereas in CD3CN 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][B9H14] (1) and [PSH][B9H14]& BULL;0.5CHCl(3) (solvated, 1 & BULL;0.5CHCl(3)) have also been studied by X-ray diffraction analysis. A solid-state NMR study has demonstrated that K[B9H14] and [PSH][B9H14] (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.

Automated summary

The [PSH](+) decaborane salt can react with ethanol to form [PSH][B9H14], providing a simple method for synthesizing the arachno-nonaborate anion. The properties of the new polyhedral salt are characterized using NMR spectroscopy and X-ray diffraction. DFT calculations reveal insights into the low-energy dynamic behavior involving hydrogen atoms.