The solid state structure of [b(10)h(11)](-) and its dynamic NMR spectra in solution

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Computational Chemistry

Background:

• The study investigates the anionic boron hydride cluster [B(10)H(11)](-).
• Understanding the structural and dynamic properties of boron clusters is crucial for developing new materials and catalysts.
• Comparison with the related [B(10)H(10)](2-) cluster provides insights into structure-property relationships.

Purpose of the Study:

• To elucidate the solid-state structure of [PPh(3)(benzyl)][B(10)H(11)] at different temperatures.
• To investigate the dynamic behavior of the [B(10)H(11)](-) anion in solution using variable-temperature NMR spectroscopy.
• To complement experimental findings with ab initio calculations.

Main Methods:

• Single-crystal X-ray diffraction at -123 °C and 24 °C.
• Variable temperature multinuclear NMR spectroscopy.
• Ab initio computational calculations.

Main Results:

• The crystal structure of [PPh(3)(benzyl)][B(10)H(11)] was determined, revealing a B(10) core similar in shape to [B(10)H(10)](2-).
• The 11th hydrogen atom asymmetrically caps a polar face of the cluster without disorder in the solid state.
• Variable temperature NMR studies demonstrated significant fluxionality of both cluster hydrogen atoms and the boron cage in solution, contrasting with the rigid [B(10)H(10)](2-) cluster.

Conclusions:

• The [B(10)H(11)](-) anion exhibits dynamic behavior in solution due to multiple exchange processes involving both hydrogen atoms and the boron cage.
• The structural and dynamic properties of [B(10)H(11)](-) differ significantly from those of the more stable [B(10)H(10)](2-) cluster.
• Experimental and computational results provide a comprehensive understanding of the fluxional nature of this anionic boron cluster.