Trennung und Charakterisierung der metallgemischten Cluster [(Nb_n Ta_6–n) Cl]²⁺, n = 0–6

Abstract

Bei der Umsetzung von NbCl5 mit Ta oder von TaCl5 mit Nb in einer NaCl‐Schmelze entstehen Verbindungen des Typs [(Nbn Ta6–n) Cl 12i]2+, n = 0–6. In wäßriger NaF‐Lösung bilden sie durch Koordination von F−− Anionen, die bei ausreichend tiefer Temperatur (–5°C) kinetisch stabil sind und sich durch mehrfache Ionenaustauschchromatographie an DEAE‐Cellulose in die einzelnen metallgemischten Cluster auftrennen lassen. Während für n = 1 und 5 die reinen Verbindungen vorliegen, handelt es sich bei n = 2, 3, 4 um Paare der geometrischen Isomeren im statistischen Mengenverhältnis. Die Cluster unterscheiden sich durch die Lage einer intensiven Charge‐Transfer‐Bande, die bei der Metallsubstitution in Schritten von etwa 12 nm von 327 (Ta6) nach 396 nm (Nb6) verschoben wird. Die bei 80 K registrierten IR‐Spektren der metallgemischten Cluster zeigen nur im Bereich der antisymmetrischen Metall–Metall‐Valenzschwingung typische Aufspaltungsmuster. Die Banden werden den Komponenten der entarteten Ttu‐Schwingung der oktaedrischen Endglieder bei 233 (Nb6) und 209 cm−1 (Ta6) zugeordnet, die aus der Erniedrigung der Symmetrie nach D4h, C4v, C3v und C2v folgen. Während die Metall–Cli‐Valenzschwingungen beim Austausch von Nb gegen Ta systematisch zu kleineren Frequenzen verschoben werden, bleiben alle Deformationsschwingungen davon unbeeinflußt.

Preparation and Spectroscopic Investigations of Mixed Octahedral Complexes and Clusters

“…The second example, [({Nb n Ta 6 - n }Cl i 12 )F a 6 ] 4- , n = 0−6, exhibits the highest degree of enrichment for the seven individual complexes, with the exception of the stereoisomers. This has been achieved by repeated UV-monitored ion exchange chromatography on DEAE cellulose and final energy dispersive X-ray microanalysis …”

“…This has been achieved by repeated UV-monitored ion exchange chromatography on DEAE cellulose and final energy dispersive X-ray microanalysis. 434 The third approach utilizes counterflow distribution over 550 steps of a statistical mixture of [(Mo 6 -{Cl i n I i 8-n })Cl a 4 ], and yields the individual species with n ) 5-7; although the geometric isomers for n ) 5 and 6 have not been separable. 435…”

“…428 With the aforementioned difficulties of vibrational and electronic spectroscopy, and the problems of separation in mind, it is clear that there are only a few examples of UV-vis, IR, and Raman investigations on mixed clusters. High enrichment by DEAE anion exchange chromatography of the species, [({Nb n Ta 6-n }Cl i 12 )F a 6 ] 4-, n ) 1-5, without separation of the stereoisomers, and work on [({Nb n -Ta 6-n }Cl i 12 )Br a 2 ]‚8H 2 O, 434 has enabled an IR, Raman, and UV-vis spectroscopic study of these compounds in comparison to the terminal members of these series, [(Nb 6 Cl i 12 )Br a 2 ]‚8H 2 O and [(Ta 6 Cl i 12 )Br a 2 ]‚ 8H 2 O. 441 The series, [B 6 Cl n Br 6-n ] 2-, [B 6 Cl n I 6-n ] 2and [B 6 Br n -I 6-n ] 2-, n ) 0-6, have also been separated by means of DEAE cellulose 429 and investigated by IR and Raman spectroscopy.…”

Atomlike Building Units of Adjustable Character: Solid‐State and Solution Routes to Manipulating Hexanuclear Transition Metal Chalcohalide Clusters

“…Such substitutions can also be accomplished by introducing an appropriate source of the second metal and adjusting the stoichiometry of a high-temperature solid-state preparation. Among the soluble cluster products stemming from reactions of this type, [Mo 6 À n W n Cl 8 F 6 ] 2À ðn ¼ 0 À 6Þ and [Nb 6 À n Ta n Cl 12 F 6 ] 4À (n ¼ 1-5) have been particularly well characterized (126,127).…”

Controlling the Deposition Process of Nanoarchitectonic Nanocomposites Based on {Nb6−xTaxXi12}n+ Octahedral Cluster-Based Building Blocks (Xi = Cl, Br; 0 ≤ x ≤ 6, n = 2, 3, 4) for UV-NIR Blockers Coating Applications

“…In order to extend these properties, the first compounds synthesized with x = 0 or 6 were prepared by W. Preetz and K. Harder for the series Na 4 [{Nb 6−x Ta x Cl i 12 }Cl a 6 ]. (1 ≤ x ≤ 5) [20]. The protocol developed by these authors consists of the reduction of a niobium or tantalum halide by tantalum or niobium, respectively, in the presence of sodium chloride.…”