The Role of Bi³⁺ in Promoting and Stabilizing Iron Oxo Clusters in Strong Acid

Abstract

Metal oxoc lusters and metal oxides assemble and precipitate from water in processes that depend on pH, temperature,a nd concentration. Other parameters that influence the structure,composition, and nuclearity of "molecular" and bulk metal oxides are poorly understood, and have thus not been exploited. Herein, we showt hat Bi 3+ drives the formation of aqueous Fe 3+ clusters,usurping the role of pH. We isolated and structurally characterized aBi/Fecluster,Fe 3 BiO 2 -(CCl 3 COO) 8 (THF)(H 2 O) 2 ,a nd demonstrated its conversion into an iron Keggin ion capped by six Bi 3+ irons (Bi 6 Fe 13 ). The reaction pathway was documented by X-ray scattering and mass spectrometry.O pposing the expected trend, increased cluster nuclearity required ap Hd ecrease instead of ap H increase.W ea ttribute this anomalous behavior of Bi/Fe(aq) solutions to Bi 3+ ,w hich drives hydrolysis and condensation. Likewise,Bi 3+ stabilizes metal oxo clusters and metal oxides in strongly acidic conditions,w hich is important in applications such as water oxidation for energy storage.

Reaction Pathway to the Only Open‐Shell Transition‐Metal Keggin Ion without Organic Ligation

“…The role of Zn 2+ in this study is reminiscent to that of Bi 3+ , driving condensation irregardless of pH; despite their substantially different radius and aqueous solubility (Bi 3+ larger with poorer solubility). Consistent with the behavior observed here, Zn 2+ has a strong tendency towards dehydration; [i.e.…”

“…Instead, they are built from heterometal fragments composed of: 1) The central tetrahedral metal plus one or more octahedral metals, or 2) A metal cation that stabilizes the cluster on the outside, linked to one or more octahedral metals (i.e. the Bi that caps the iron Keggin ion or Zn that caps δ‐ZnCr 12 , reported here). Despite the similar reaction pathways of these Keggin anions and cations of different compositions, they require vastly different reaction conditions.…”

Iron Aquo Complex as an Efficient and Selective Homogeneous Photocatalyst for Organic Synthetic Reactions

“…This is the first report showing the potential of such simple, cheap iron ions as homogeneous photocatalyst for practical organic synthesis. The recent progress made in finding of molecular level iron ions in aqueous solutions, will make photocatalytic organic synthesis using iron catalysis more attractive and feasible.…”

Capturing Lacunary Iron–Oxo Keggin Clusters and Insight Into the Keggin‐Fe13 Cluster Rotational Isomerization

“…In the nonclassic growth mode, the formation of the ferrihydrite is regarded ast he aggregationo fp renucleation clusters, rather than atom-by-atomg rowth. [13][14][15][16][17][18][19][20] With capturing of the Keggin-Fe 13 clusters in water, [14,15,20,21] especiallyt he experimental evidence of Keggin-Fe 13 clusters as precursor of the ferrihydrite formation,t he nonclassic growth mode has been widely adopted in the literature. [13,14,[16][17][18][19][20][21] Althought he single phase modelo ft he ferrihydrite [13] clearly demonstrates that ferrihydrite consistso fd-Fe 13 Kegginu nits, it remains unclear why the Keggin-Fe 13 cluster can undergo rotational isomerization ( Figure 1).…”

“…[13][14][15][16][17][18][19][20] With capturing of the Keggin-Fe 13 clusters in water, [14,15,20,21] especiallyt he experimental evidence of Keggin-Fe 13 clusters as precursor of the ferrihydrite formation,t he nonclassic growth mode has been widely adopted in the literature. [13,14,[16][17][18][19][20][21] Althought he single phase modelo ft he ferrihydrite [13] clearly demonstrates that ferrihydrite consistso fd-Fe 13 Kegginu nits, it remains unclear why the Keggin-Fe 13 cluster can undergo rotational isomerization ( Figure 1). [14,20] In an effort to answer this question,N yman andc o-workers, [14] based on the comparison of the pair distance distribution function of Bi 6 Fe 13 L 12 dissolved in ethanolw ith that of two simulated dimers (the dimer of dodecaniobate a-Keggin ions linked by as ingle alkali, [22] and the dimer derived from the ferrihydrites tructure), deduced that the conversion of Keggin-Fe 13 clusters to ferrihydrite probablyi nvolvesl acunary Keggin-Fe 13 clusters.…”