Neutral Adducts of Molybdenum Hexafluoride: Structure and Bonding in MoF(NCH) and MoF(NCH).

The first Lewis acid base adducts of MoF and an organic base have been synthesized, i. e., MoF(NCH) and MoF(NCH). These adducts are structurally characterized with X-ray crystallography, showing that both adducts adopt capped trigonal prismatic structures. The MoF(NCH) and MoF(NCH) adducts are fluxional on the NMR time scale at room temperature. Two different fluorine environments could be resolved by F NMR spectroscopy at -80 °C for the 1 : 2 adduct, MoF(NCH), whereas MoF(NCH) remains fluxional at that temperature. Density functional theory (DFT) calculations aide the assignment of the infrared and Raman spectra. Natural Bond Order and Molecular Electrostatic Potential analyses elucidate the structures and properties of the MoF pyridine adducts. Regions of significantly higher molecular electrostatic potential, i. e., σ-holes, in trigonal prismatic compared to octahedral MoF rationalize the capped trigonal prismatic geometry of the adducts. Whereas MoF(NCH) is stable at room temperature under exclusion of moisture, MoF(NCH) decomposes at 60 °C in pyridine solvent, and the solid slowly decomposes at room temperature after 24 h.