3-Pyridylacetonitrile-ligated 11-vertex rhodathiaboranes: synthesis, characterization, and X-ray crystal structure

The reaction between the 11-vertex rhodathiaborane [8,8-(PPh₃)₂-nido-8,7-RhSB₉H₁₀] (1) and 3-pyridylacetonitrile affords the hydrorhodathiaborane [8,8,8-(PPh₃)₂H-9-(3-Py-CH₂CN)-nido-8,7-RhSB₉H₉] (2) in good yield. Treatment of this cluster with ethylene leads to the formation of red, [1,1-(PPh₃)(η²-C₂H₄)-3-(3-Py-CH₂CN)-closo-1,2-RhSB₉H₈] (3). Both 11-vertex polyhedral boron-based clusters have been characterized by multielement NMR spectroscopy. In addition, (3) has been analyzed by single-crystal X-ray diffraction analysis and is only the second ethylene-ligated metalla-heteroborane to be characterized in the solid state. The molecular structure of this cluster is based on an octadecahedron. In the crystal lattice, the individual clusters form layers supported by short edge-to-face π-interactions between the phenyl rings of neighboring molecules.