Hexanuclear Niobium Cluster Complex Anions with Acetato Ligands on Intramolecular Bridging Sites: [Nb₆Clⁱ₄(OAc)ⁱ₈Cl^a₆]^2– and [Nb₆(OAc)ⁱ₁₂Cl^a₆]^2–

Abstract

From the reaction of [Nb6Cl14(H2O)4]·4H2O with acetic anhydride in the presence of an excess of (nBu4N)F the novel cluster compounds (nBu4N)2[Nb6Cli4(OAc)i8Cla6] (1) and (nBu4N)2[Nb6(OAc)i12Cla6] (2) (OAc = acetato ligand) are obtained. They are the first examples of hexanuclear niobium cluster compounds with acetato ligands on the inner sites of the metal atom octahedron. The crucial role of the presence of fluoride ions in the synthesis is discussed. Each acetato ligand bridges in a μ2‐η1‐fashion with one O atom an edge of the metal atom octahedron. The monoclinic crystals of 1 consist of discrete (nBu4N)+ cations and [Nb6Cli4(OAc)i8Cla6]2– cluster anions. They are oxidized by two electrons with respect to the cluster starting material. Besides the syntheses of 1 and 2, the structure of 1 and spectral properties of both compounds are reported.

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

“…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.…”

Hexanuclear Niobium Cluster Alcoholates – First Representatives with Isopropanolato Ligands

“…Thereby, 3 (and 4 ) are the first representatives of reduced niobium alcoholates with isopropanolato ligands. All compounds but 1 contain 14 CBE cluster cores, as do all the other so far known Nb 6 cluster compounds with O‐donor functions on inner coordination sites [25–27,35] . The stability of the higher oxidation state of the cluster core likely is related to the higher Pearson hardness of the O donor ligand compared to Cl, Br, or I [36] .…”

“…All compounds but 1 contain 14 CBE cluster cores, as do all the other so far known Nb 6 cluster compounds with O-donor functions on inner coordination sites. [25][26][27]35] The stability of the higher oxidation state of the cluster core likely is related to the higher Pearson hardness of the O donor ligand compared to Cl, Br, or I. [36] The cluster anion in 2 has all inner sites occupied by ethanolato ligands, as decribed by the formula [Nb .…”