The chemistry of cobalt acetate—IV. The isolation and crystal structure of the symmetric cubane, tetrakis[(μ-acetato)(μ3-oxo) (pyridine)cobalt(III)] · chloroform solvate, [Co4(μ3-O)4(μ-CH3CO2)4(C5H5N)in4] · 5CHCl3 and of the dicationic partial cubane, trimeric, [(μ-acetato)(acetato)tris(μ-hdyroxy(μ3-oxo) hexakispyridinetricobalt(III)]hexafluorophosphate · water solvate, [Co3(μ3-O)(μ-OH)3(μ-CH3CO2(CH3CO2(C5H5N)6[PF6]2 · 2H2O

Biohybrid Systems for Improved Bioinspired, Energy‐Relevant Catalysis

“…Similarly, Dismukes and co‐workers synthesized a cubic Co III 4 O 4 cluster, Co 4 O 4 (OAc) 4 (py) 4 , as an efficient water oxidizing catalyst (py=pyridine) (Figure 1c) [46] . Such a structure was previously reported by Beattie et al., isolated from cobalt(II) acetate in solution using pyridine co‐ligands [47] . However, Nocera and co‐workers demonstrated that the existence of Co II impurities are primarily responsible for water oxidation in near‐neutral buffered aqueous solutions [48] .…”

“…[46] Such a structure was previously reported by Beattie et al, isolated from cobalt(II) acetate in solution using pyridine co-ligands. [47] However, Nocera and co-workers demonstrated that the existence of Co II impurities are primarily responsible for water oxidation in nearneutral buffered aqueous solutions. [48] Indeed, Tilley and coworkers found that, after careful removal of Co II impurities by column chromatography and treatment with tetrasodium diaminoethanetetracarboxylate (Na 4 EDTA), the cubane complex did not exhibit noticeable catalysis over a range of pH's between 4 and 10.…”

Molecular Cobalt Clusters as Precursors of Distinct Active Species in Electrochemical, Photochemical, and Photoelectrochemical Water Oxidation Reactions in Phosphate Electrolytes

“…Inspired by the cubane structure of the natural oxygen evolution catalyst( OEC) Mn 3 Ca(m-O) 4 , [1] investigationso fp otential OECs with analogous cubane motifs have attracted considerable attention, and severalr eportso ft he water oxidation reaction (WOR) catalyzed by molecular OECs with ac ubane motif have appeared recently. [2] However,a ni ncreasingly common topic of debate regardingmolecular OECs is the nature of the "real active species" for the WOR and whether the cubane motif is essential, as in some cases the catalysts were shown to be "species"g enerated from molecular precursors.…”

“…[2i, 5] The cubane motif is supposed to be an essential unit for the photochemical WOR on the basis of the observation that no activity was found with materials based on the incomplete cobalt cubane, dimer,a nd trimer motifs. [6] However, it was reportedr ecently that cobalt cubane species, [Co 4 (m 3 -O) 4 (m-OAc) 4 L 4 ]( L = substitutedp yridine), are not active for the electrochemical WOR, with the catalytic behaviora ttributed to Co II impurities. [3a] These conflicting resultsa re furtherc omplicated by the observation that the molecular OEC and the derived "real active species"w ere very sensitive to the WOR methodologies and experimental conditions.…”

“…[3a] These conflicting resultsa re furtherc omplicated by the observation that the molecular OEC and the derived "real active species"w ere very sensitive to the WOR methodologies and experimental conditions. [2g, 7] Here, we report the catalyticb ehavioro ft hree model cobalt (III) acetate compounds, representative of tetrameric, trimeric, and dimeric oligomers, namely [Co 4 O 4 (OAc) 4 py 4 ]( Co-cubane), [Co 3 (m 3 -O)(m-OAc) 6 py 3 ]PF 6 (Co-trimer), and [Co 2 (m-OH) 2 (m-OAc)-(OAc) 2 py 4 ]PF 6 (Co-dimer), respectively, for the WOR under electrochemical, photochemical, and photoelectrochemical conditions.A na queous phosphate electrolyte was employed in this researchb ecause it is widelyu sed for the WOR. The catalytic behavior of cobalt compounds for the WOR was found to be highlyd ependent on the cobalt compound structure and WOR methodologies, as shown in Scheme1.C o-cubane and Codimerw ere not active for the electrochemical WOR to 1.4 V Scheme1.Structures and catalytic behaviors of the model cobalt compounds in the three WOR systems.…”