An Unprecedented Tetranuclear Niobium Aqua Ion with a Capping μ₄-Sulfido Ligand

Abstract

The aqueous solution chemistry of niobium is rather unexplored, and well characterized aqua complexes are scarce. In this work, a new niobium aqua ion is obtained upon treatment of Zn-reduced ethanolic solutions of NbCl5 with HCl in the presence of a sulfide source. The red aqua ion, obtained upon cation-exchange chromatography, forms readily the thiocyanate complex which has been crystallized as Cs(4.26)Na(1.74)[Nb4SO5(NCS)10] . 0.33H2O. X-ray crystallography revealed an unprecedented metal-metal bonded tetranuclear Nb4(mu4-S)(mu2-O)5(4+) core with a capping mu4-S ligand.

A Novel Niobium Cluster Aqua Ion with Capping μ4‐Se Ligand

“…The first type of Nb (Nb1, Nb3) atom is bonded to three NCS – , two μ 2 ‐O and one μ 4 ‐Se, whereas the second type of Nb (Nb2, Nb4) atom is bound with two NCS – , three μ 2 ‐O and one μ 4 ‐Se. The Nb–Nb bond lengths of 2.8314(17)–2.9016(17) Å are much longer than the those of the Nb 3 core in [Nb 3 SO 3 (NCS) 9 ] 6– (2.763 Å), but are very similar to those found in related thiocyanate complexes [Nb 4 (μ 4 ‐S)(μ 2 ‐O) 5 (NCS) 10 ] 6– (2.802–2.867 Å), [Nb 5 (μ 3 ‐S) 2 (μ 3 ‐O) 2 (μ 2 ‐O) 2 (NCS) 14 ] 6– (2.800–2.911 Å), and [Nb 2 S 4 (NCS) 8 ] 4– (2.867 Å) . The Nb–Se bond lengths of 2.5310(18)–2.6388(17) Å are shorter than the those of the dinuclear {Nb 2 Se 4 } clusters with Se 2 2– bridge ligands.…”

“…The Nb–O [1.943(11)–2.065(10) Å] and Nb–N [2.128(12)–2.212(14) ] bond lengths ranges are not significantly different from those of the [Nb 3 SO 3 (NCS) 9 ] 6– , [Nb 4 (μ 4 ‐S)(μ 2 ‐O) 5 (NCS) 10 ], 6– and [Nb 5 (μ 3 ‐S) 2 (μ 3 ‐O) 2 (μ 2 ‐O) 2 (NCS) 14 ] 6– , …”

“…Aqua complexes of niobium are rare and generally less stable with respect to oxidation and hydrolysis , . Nb V has a well‐known propensity to form polynuclear oxo‐anionic species, and Nb II ‐Nb IV tend to form M–M bonded cluster complexes.…”

“…Another approach to niobium aqua complexes consists in the reduction of NbCl 5 in ethanol with zinc or aluminum followed by treatment with aqueous acids. In addition to the trinuclear aqua complexes of {Nb 3 XO 3 } type, such as unique organometallic trinuclear niobium cluster complex with unusual perpendicularly coordinated μ 3 ‐η 2 :η 2 (⊥)‐acetonitrile ligand, [Nb 3 (μ‐η 2 :η 2 ‐NCCH 3 )O 3 (H 2 O) 9 ] 6+ , it gives, in the presence of S 2– , unprecedented tetra‐ and pentanuclear aqua ions, [Nb 4 (μ 4 ‐S)(μ 2 ‐O) 5 (H 2 O) 10 ] 4+ and [Nb 5 (μ 3 ‐S) 2 (μ 3 ‐O) 2 (μ 2 ‐O) 2 (H 2 O) 14 ] 8+ , which were isolated and characterized in detail, including X‐ray structures of their thiocyanate derivatives , . This opens up exciting possibilities of doing oxo‐sulfido or related niobium cluster chemistry in aqueous solutions.…”

Oxygen, sulfur, selenium and tellurium

“…63 Mono-, bi-and tetranuclear platinum group metal complexes of cyanodiselenoimidocarbonate, [C 2 N 2 Se 2 ] 2-, and triselenocarbonate, [CSe 3 ] 2were prepared by Woollins and co-workers, 64,65 , which was formulated on the basis of UV-Vis, RR and crystallography to possess a bis(m-S 2 dÀ ) dicopper(II) core, 68 the tetranuclear niobium complex [Nb 4 SO 5 (NCS) 10 ] 6is capped by a m 4 -sulfido ligand. 69 The counterion and crystallisation solvent are the dominant factors in determining the solid-state structures of [9]aneS 3 and [18]aneS 6 complexes of platinum(II), 70 while the first mononuclear selenoaroyl complexes were prepared from molybdenum alkylidyne precursors using mesityl isoselenocyanate. 71 The bicyclic system CF 3 CN 5 S 3 is a monodentate donor through its N5 atom with Zn 21 , Co 21 and Cu 21 , whereas with cadmium(II) bidentate co-ordination (the nitrogen atom adjacent to carbon is the second donor) is supplemented by a CdÁ Á ÁF interaction.…”