Polyhedral monocarbaborane chemistry: Reactions of the [6-Ph-nido-6-CB9H11]− anion with two-electron donors to yield a series of neutral arachno and closo ten-vertex monocarbaborane derivatives

Reaction of the ten-vertex [6-Ph-nido-6-CB9H11]− anion (1) with two-electron donor ligands L, where L is SMe2, NH2Ph, NC5H5, NC5H4-para-CH2Ph, NC5H4-para-Ph or NC9H7 (where NC9H7 is quinoline) in the presence of {FeCl3(OH2)6} gives the six neutral arachno ten-vertex monocarbaboranes [6-Ph-9-L-arachno-6-CB9H12], compounds 2, 3, 4, 7, 9 and 11, respectively, isolatable in yields of up to 63%. On prolonged treatment with {FeCl3(OH2)6} oxidative cluster closure of the four compounds 4, 7, 9 and 11 that have pyridine-type ligands gives the neutral closo ten-vertex monocarbaboranes [1-Ph-6-L-closo-1-CB9H8], compounds 6, 8, 10 and 12, respectively, in yields of 49–92%. All new species 2, 3, 4, 6, 7, 8, 9, 10, 11 and 12 are characterised by single-crystal X-ray diffraction analysis and NMR spectroscopy. [This paper is an annotated exposition of parts of an oral presentation at the Third Pan-European Meeting of Boron Chemists, EUROBORON-3, Pruhonice, The Czech Republic, September 2004, of which the proceedings constitute this volume of Journal of Organometallic Chemistry.]