New Hexanuclear Niobium Cluster Compounds with Perfluorinated Ligands Made Using Ionic Liquids

Abstract

Three new hexanuclear niobium cluster compounds, which carry trifluoroacetate ligands on the exo sites of the metal atom octahedra, were synthesized and characterized. For the syntheses, the ionic liquid 1,1,3,3-tetramethylguanidinium-trifluoroacetat, (TMG-H)TFA, was used as solvent as well as source for the ligands and cations. All three cluster compounds consist of the [Nb 6 Cl 12 (TFA) 6 ] 4anion and (TMG-H) + , (TMG-H) + + (TMGTFAA-H) + , or (TMGTFAA-H) + cations [(TMGTFAA-H) + = 1,1,3,3-tetramethylguanidine-trifluoroacetamidinium]. TMGTFAA and the corresponding cation are obtained * Prof. Dr. M. Köckerling

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.…”

Octahedral {Ta6I12} Clusters

“…Yield: 48%. Anal Calcd for Ta 6 I 14 ( [Ta 6 I 12 (H 2 O) 6 ]@PSS (7). A 250 mL portion of an aqueous solution of [Ta 6 I 12 (H 2 O) 6 ]I 2 (0.0005 mol/L) was mixed with 120 mg of PSS (2200 kDa), and this suspension was stirred for 6 h to achieve complete solubilization of PSS.…”

“…Modern developments have been repeatedly reviewed in various depths. − Recently the scope of this chemistry has been expanded by the introduction of methoxide, CH 3 O – , as bridging ligands, as well as by use of organic solvents and ionic liquids as reaction media. − Chihara and Kamiguchi have shown that solid halide clusters of Nb and Ta, taken as [M 6 Cl 12 (H 2 O) 4 Cl 2 ], are strong Brønsted acids and catalyze isomerization of olefins, dehydrohalogenation of alkyl halides, ring-attachment isomerization and dealkylation of diethylbenzenes, dehydration of alcohols, alkylations, heterocyclizations, and other organic reactions at elevated temperatures. , Within the scope of cluster materials, tetrathiafulvalenium-based organic cation radicals form salts with paramagnetic [Nb 6 Cl 18 ] 3– , in which there is mixing of the spins of the cluster and cation. , [Nb 6 Cl 12 Br 6 ] 3– , when it is absorbed on gold layers, transfers the electron density from the cluster to the metal surface, while solutions of [Nb 6 Cl 18 ] 3– are capable of dissolving gold films . These and other findings demonstrate that these clusters can efficiently modify gold and silver surfaces.…”