[Nb6Cl14(pyrazine)4], a Versatile Precursor for Ligand-Supported Hexanuclear Niobium Cluster Compounds: Synthesis, Characterization, Follow-Up Reactions, and Intermolecular Interactions

The compound [Nb6Cl14(pyrazine)4]·2CH2Cl2 (1) was investigated for its suitability as a starting compound for new ligand-supported hexanuclear niobium cluster compounds. The synthesis, stability to air and increased temperature, solubility and usability for subsequent reactions of 1, and purification and separation of the reaction products are discussed. The compounds with cluster units [Nb6Cl14L4], where L = iso-quinoline N-oxides (2), 1,1-dimethylethylenediamines (3), or thiazoles (4), and [Nb6Cl14(PEt3)3.76(Et3PO)0.24]­[Nb6Cl14(MeCN)4]·4MeCN (5) are presented as follow-up products. The crystal structures of compounds 1–5 are analyzed, and the structures are discussed with respect to their intra- and intermolecular bonding situations and crystal packing. In addition to hydrogen bonds and π–π interactions, the appearance of chalcogen and halogen bonds and lone pair−π interactions between Nb6 cluster units was observed for the first time.