Cluster Salts [Nb6Cl12(HIm)6]An (with HIm=1H-imidazole and A=Mineral Acid Anion, n=1 or 2) Made in and with Bronsted-basic Ionic Liquids and Liquid Mixtures

Four new hexanuclear niobium cluster compounds of the general formula [Nb6Cl12(HIm)(6)](A)(n) . x(solvent molecule) (HIm=1H-imidazole, A=mineral acid anion, Cl- (n=2) (1), (SO4)(2-) (n=1) (2), (CrO4)(2-) (n=1) (3), and (HAsO4)(2-) (n=1) (4)) were prepared. Their synthesis can be done in basic ionic liquids, which form on the addition of a mineral acid, which also delivers the counter anion for the final cluster compound, to an excess of the 1H-imidazole. Some addition of an auxiliary solvent, like methanol, improves the speed of crystallisation. The cluster unit comprises a hexanuclear Nb-6 unit of octahedral shape with the edges bridged by Cl atoms and the exo sites being occupied by N-bonded 1H-imidazole ligands. The cluster cation carries sixteen cluster-based electrons. Between the NH groups of the ligands of the cluster unit, the anions and the co-crystallised water (1), or 1H-imidazole and methanol molecules (2, 3, and 4) a network of hydrogen bonds exists.

Automated summary

Four new hexanuclear niobium cluster compounds were synthesized in basic ionic liquids with the addition of a mineral acid, which also provided the counter anion. The addition of an auxiliary solvent like methanol improved the crystallization speed. The cluster unit consists of a hexanuclear Nb-6 unit with octahedral shape and N-bonded 1H-imidazole ligands.