Molecular niobium(v) complexes with mononuclear {Nb₁} and dinuclear oxo species {Nb₂O} connected through aryl di- or tetra-carboxylate linker

Abstract

Several aryl polycarboxylic ligands (pyromellitic acid, 4,4’-azobenzenedicarboxylic acid and 3,3’,5,5’-azobenzenetetracarboxylic acid) have been used to react with the pentavalent ethoxide niobium(V) precursor Nb(OEt)5. Three new crystalline molecular compounds (1 with...

Isolation of a Dodecanuclear Polyoxo Cluster {Nb12O21} Showing a Rare Case of Five‐fold Coordinated Niobium(V) Centers with a Square Pyramidal Geometry

“…The formation of an ester due to the esterification mentioned earlier could be confirmed by the presence of vibration in the range 1710–1695 cm −1 . They appear to be extremely weak in this case and are not always observed in this kind of mixtures [51] …”

“…They appear to be extremely weak in this case and are not always observed in this kind of mixtures. [51] However, there is no evidence of the presence of the {Nb 12 } compound in the supernatant solutions. The ν(C=O) and ν(COO) vibrations are summarized in Table 1.…”

“…It led to the formation of an hexadecaniobate cluster [Nb 16 O 28 (OEt) 12 (piv) 12 ] [49] . In our recent work on this topic, we have used several aromatic monocarboxylic and polycarboxylic acid ligands to complex niobium(IV) tetrachloride and niobium(V) ethoxide precursors, successfully increasing the nuclearity of the niobium centers in the final compounds up to the formation of an octameric {Nb 8 O 12 } moieties [50–52] …”

“…[49] In our recent work on this topic, we have used several aromatic monocarboxylic and polycarboxylic acid ligands to complex niobium(IV) tetrachloride and niobium(V) ethoxide precursors, successfully increasing the nuclearity of the niobium centers in the final compounds up to the formation of an octameric {Nb 8 O 12 } moieties. [50][51][52] In this contribution, we report on the investigation of the reactivity of the anthracene-9-carboxylic acid ligand with niobium(IV) tetrachloride NbCl 4 (THF) 2 precursor as the niobium(IV) source. The reaction occurring in isopropanol solvent at 120 °C leads to the formation of a molecular crystalline compound containing niobium(V) centers involved in two distinct {Nb 12 � 7(HO i Pr) where the two distinct dodecamers are contained in the same crystal structure, but with different coordination environments for some niobium centers, which can be six-fold or five-fold oxo-surrounded.…”

Not So Similar: Different Ways of Nb(V) and Ta(V) Catecholate Complexation

“…Recently, we have added novel photoactive salts into this family [23] and reported a binuclear oxalate complex [Nb 2 O 2 (C 2 O 4 ) 4 (µ-C 2 O 4 )] 4− [24]. Outside the oxalate field, Loiseau et al reported interesting examples of polynuclear niobium(V)-based carboxylate oxo complexes obtained by controlled hydrolysis of [Nb(OEt) 5 ] in the presence of different carboxylic acids [25,26]. Among the few non-carboxylate complexes, there are two structurally characterized complexes of M(V), which should be taken into consideration.…”