Nido-6-metalladecaborane chemistry: Molecular structure and fluxionality of [6,6,6,6-(CO)2(PPh3)2-nido-6-WB9H13]

The molecular and crystal structure of the nido-6-tungstadecaborane [6,6,6,6-(CO)2(PPh3)2-nido-6-WB9H13] (1) has been determined showing that the tungsten atom is incorporated into the 6-position of a nido 10-vertex (WB9) cage. The tungsten atom has a seven-coordinate capped trigonal prismatic environment and is bonded to two hydrogen and three boron atoms of the {B9H13} cage, in addition to two CO groups and two PPh3 ligands. Variable-temperature (−90°C to +50°C) 31P{1H} NMR spectroscopy of 1 reveals that the exo-polyhedral ligands about the tungsten atom are fluxional with respect to PPh3 site exchange with an activation energy (ΔG‡), at the coalescence temperature (−73°C), of <38 kJ mol−1.