Air-Stable, Well-Soluble AI2[Nb6Cl18] Cluster Compounds (AI = Organic Cation): A New Route for Preparation, Single-Crystal Structures, Properties, and ESI-Mass Spectra

Abstract

Five niobium cluster compounds of the AI2[Nb6Cl18] type (AI = organic cation: [nPr4N]+, [nBu4N]+, [BMIm]+, [Ph4P]+, and [PPN]+) are obtained through treatment of [Nb6Cl14(H2O)4]·4H2O with excess of thionyl chloride in the presence of an organic chloride, AICl. Single-crystal structure studies show that the compounds consist of discrete cations and cluster [Nb6Cl18]2– anions. The cluster unit of the hydrated cluster starting material is oxidized by two electrons. Powder diffraction studies and NMR spectroscopic measurements show all compounds to crystallize without co-crystallized solvent molecules. They are air and water stable. The solubility in organic solvents changes to a great extent on changing the type of cation. The ESI-MS spectra of [nPr4N]2[Nb6Cl18] and [Ph4P]2[Nb6Cl18] show the pseudomolecular peak of the anionic cluster as well as additional signals, which involve simultaneously chloride mass loss and reduction processes