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

Abstract

The compound [Nb 6 Cl 14 (pyrazine) 4 ]•2CH 2 Cl 2 (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 [Nb 6 Cl 14 L 4 ], where L = iso-quinoline N-oxides (2), 1,1-dimethylethylenediamines (3), or thiazoles (4), and [Nb 6 Cl 14 (PEt 3 ) 3.76 (Et 3 PO) 0.24 ]-[Nb 6 Cl 14 (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 intraand 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 Nb 6 cluster units was observed for the first time.

Cluster Compounds with Oxidised, Hexanuclear [Nb6Cli12Ia6]n− Anions (n=2 or 3)

“…This successful concept of treating [Nb 6 Cl i 12 X a 2 (H 2 O) a 4 ] ⋅ 4H 2 O ( X =Cl or I) with a water scavenger acting as reactant, solvent and oxidiser, and supplying further ligands has been introduced before. [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ] All four investigated compounds are obtained in high yield. The experimental conditions for the synthesis of 1 to 4 are summarized in Scheme 1 .…”

“…If a mixture of Ac 2 O, CH 2 Cl 2 , and (TMS)I is used, a two‐electron oxidation is achieved, leading to the 14 CBE‐containing [Nb 6 Cl i 12 I a 6 ] 2− units. This successful concept of treating [Nb 6 Cl i 12 X a 2 (H 2 O) a 4 ] ⋅ 4H 2 O ( X =Cl or I) with a water scavenger acting as reactant, solvent and oxidiser, and supplying further ligands has been introduced before [42–50] . All four investigated compounds are obtained in high yield.…”

“…Because of the presence of two distinct different coordination spheres, inner (i) and outer (a) in [M 6 X i 12 X a 6 ] type cluster compounds, we started to search for preparative procedures for mixed chloride-iodidesupported cluster complexes with only one halide type on each of the two different coordination site types, that is, cluster ) with a water scavenger acting as reactant, solvent and oxidiser, and supplying further ligands has been introduced before. [42][43][44][45][46][47][48][49][50] All four investigated compounds are obtained in high yield. The experimental conditions for the synthesis of 1 to 4 are summarized in Scheme 1.…”