Discrete Neutral Niobium Cluster Units in Compounds of the Type [Nb₆Cl₁₄L₄] with L = O or N Donor Ligand

Abstract

Six new hexanuclear niobium cluster compounds of the general formula [Nb 6 Cl 14 L 4 ]·x(solvent molecule) [L = neutral O or N donor ligand, x = 0-2.5; pyrimidine (1), 1-methyl imidazole (2), isobutyronitrile (3), isopropyl alcohol (4), triphenylphosphine oxide (5), dimethyl sulfoxide (6)] were prepared. The syntheses were carried out by dehydration of the precursor [Nb 6 Cl 14 (H 2 O) 4 ]·4H 2 O with different water scavangers, like acetic anhydride, trimethyl acetic anhydride and diethylcarbonate in the presence of the corresponding neutral ligand.

[Nb6Cl12(HIm)6](OAc)2·3MeOH – a hydrogen-bonded network of niobium cluster cations, acetate anions and methanol molecules

“…The average Nb-Nb (2.928 Å) and Nb-Cl i distances (2.462 Å) are in good agreement with the distances in known compounds with niobium cluster cations of the composition [Nb 6 Cl 12 L 6 ] 2+ , as found in the literature [16,17]. Also, the average Nb-N distance (2.293 Å) is found in the range of the distances in known compounds with other azole coordinated niobium cluster units [14]. All six imidazole ligands, coordinated to the niobium cluster cation, form hydrogen bonds.…”

“…The occupation with four neutral ligands (L) and two anionic ligands results in the formation of neutral cluster units of the formula [Nb 6 Cl 14 L 4 ]. With six neutral ligands being bonded to the exo-sites, niobium cluster cations are formed [11][12][13][14]. To the best of our knowledge, the crystal structures of only four compounds with a [Nb 6 Cl i…”

[Nb6Cl12(CH3OH)4(OCH3)2] ⋅ DABCO ⋅ 1.66 CH2Cl2: Cluster Units Wrapped in a Network of Hydrogen Bonds

“…These metal-metal distances are found in the lower range of those, typically found for non-oxidized Nb 6 cluster species with 16 delocalized cluster-based electrons (CBE's). [6] This electron number is also consistent with the NbÀ Cl i distances, averaging at 2.462 Å. For the NbÀ O distances, the two ones within the equatorial plane (Nb1À O1 and Nb2À O2) are significantly shorter (2.175 Å) than that within the apical direction (Nb3À O3A, 2.251 Å).…”

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 .…”