Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution
C. André Ohlin, Stephen J. Harley, J. Gregory McAlpin, Rosalie K. Hocking, Brandon Q. Mercado, Rene L. Johnson, Eric Villa, Mary Kate Fidler, Marilyn M. Olmstead, Leone Spiccia, R. David Britt, William H. Casey
Polyoxometalate ions are used as ligands in water-oxidation processes related to solar energy production. An important step in these reactions is the association and dissociation of water from the catalytic sites, the rates of which are unknown. Here we report the exchange rates of water ligated to Co II atoms in two polyoxotungstate sandwich molecules using the 17O-NMR-based Swift-Connick method. The compounds were the [Co 4(H2O)2(B-α-PW9O 34)2]10- and the larger αββ α-[Co4(H2O)2(P2W 15O56)2]16- ions, each with two water molecules bound trans to one another in a CoII sandwich between the tungstate ligands. The clusters, in both solid and solution state, were characterized by a range of methods, including NMR, EPR, FT-IR, UV-Vis, and EXAFS spectroscopy, ESI-MS, single-crystal X-ray crystallography, and potentiometry. For [Co4(H2O)2(B-α-PW 9O34)2]10- at pH 5.4, we estimate: k298=1.5(5)±0.3à- 106 s-1, ΔH≠=39.8±0.4 kJmol-1, ΔS ≠=+7.1±1.2 Jmol-1K-1 and ΔV≠=5.6 ±1.6 cm3mol-1. For the Wells-Dawson sandwich cluster (αββα-[Co4(H 2O)2(P2W15O56) 2]16-) at pH 5.54, we find: k298=1.6(2) ±0.3à- 106 s-1, ΔH≠=27. 6±0.4 kJmol-1 ΔS≠=-33±1.3 Jmol -1K-1 and ΔV≠=2.2±1.4 cm 3mol-1 at pH 5.2. The molecules are clearly stable and monospecific in slightly acidic solutions, but dissociate in strongly acidic solutions. This dissociation is detectable by EPR spectroscopy as S=3/2 Co II species (such as the [Co(H2O)6]2+ monomer ion) and by the significant reduction of the Co-Co vector in the XAS spectra.
Chemistry - A European Journal
https://doi.org/10.1002/chem.201003550
Cobalt compounds
Paramagnetic resonance
Extended X ray absorption fine structure spectroscopy
X ray crystallography
Association reactions
Ohlin, C. A., Harley, S. J., McAlpin, J. G., Hocking, R. K., Mercado, B. Q., Johnson, R. L., ... Casey, W. H. (2011). Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution. Chemistry - A European Journal, 17(16), 4408-4417. https://doi.org/10.1002/chem.201003550
Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution. / Ohlin, C. André; Harley, Stephen J.; McAlpin, J. Gregory; Hocking, Rosalie K.; Mercado, Brandon Q.; Johnson, Rene L.; Villa, Eric; Fidler, Mary Kate; Olmstead, Marilyn M.; Spiccia, Leone; Britt, R. David; Casey, William H.
In: Chemistry - A European Journal, Vol. 17, No. 16, 11.04.2011, p. 4408-4417.
Ohlin, CA, Harley, SJ, McAlpin, JG, Hocking, RK, Mercado, BQ, Johnson, RL, Villa, E, Fidler, MK, Olmstead, MM, Spiccia, L, Britt, RD & Casey, WH 2011, 'Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution', Chemistry - A European Journal, vol. 17, no. 16, pp. 4408-4417. https://doi.org/10.1002/chem.201003550
Ohlin CA, Harley SJ, McAlpin JG, Hocking RK, Mercado BQ, Johnson RL et al. Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution. Chemistry - A European Journal. 2011 Apr 11;17(16):4408-4417. https://doi.org/10.1002/chem.201003550
Ohlin, C. André ; Harley, Stephen J. ; McAlpin, J. Gregory ; Hocking, Rosalie K. ; Mercado, Brandon Q. ; Johnson, Rene L. ; Villa, Eric ; Fidler, Mary Kate ; Olmstead, Marilyn M. ; Spiccia, Leone ; Britt, R. David ; Casey, William H. / Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution. In: Chemistry - A European Journal. 2011 ; Vol. 17, No. 16. pp. 4408-4417.
@article{25edb37e2ab14aabad1493ea4b4b6ea5,
title = "Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution",
abstract = "Polyoxometalate ions are used as ligands in water-oxidation processes related to solar energy production. An important step in these reactions is the association and dissociation of water from the catalytic sites, the rates of which are unknown. Here we report the exchange rates of water ligated to Co II atoms in two polyoxotungstate sandwich molecules using the 17O-NMR-based Swift-Connick method. The compounds were the [Co 4(H2O)2(B-α-PW9O 34)2]10- and the larger αββ α-[Co4(H2O)2(P2W 15O56)2]16- ions, each with two water molecules bound trans to one another in a CoII sandwich between the tungstate ligands. The clusters, in both solid and solution state, were characterized by a range of methods, including NMR, EPR, FT-IR, UV-Vis, and EXAFS spectroscopy, ESI-MS, single-crystal X-ray crystallography, and potentiometry. For [Co4(H2O)2(B-α-PW 9O34)2]10- at pH 5.4, we estimate: k298=1.5(5)±0.3{\`a}- 106 s-1, ΔH≠=39.8±0.4 kJmol-1, ΔS ≠=+7.1±1.2 Jmol-1K-1 and ΔV≠=5.6 ±1.6 cm3mol-1. For the Wells-Dawson sandwich cluster (αββα-[Co4(H 2O)2(P2W15O56) 2]16-) at pH 5.54, we find: k298=1.6(2) ±0.3{\`a}- 106 s-1, ΔH≠=27. 6±0.4 kJmol-1 ΔS≠=-33±1.3 Jmol -1K-1 and ΔV≠=2.2±1.4 cm 3mol-1 at pH 5.2. The molecules are clearly stable and monospecific in slightly acidic solutions, but dissociate in strongly acidic solutions. This dissociation is detectable by EPR spectroscopy as S=3/2 Co II species (such as the [Co(H2O)6]2+ monomer ion) and by the significant reduction of the Co-Co vector in the XAS spectra.",
author = "Ohlin, {C. Andr{\'e}} and Harley, {Stephen J.} and McAlpin, {J. Gregory} and Hocking, {Rosalie K.} and Mercado, {Brandon Q.} and Johnson, {Rene L.} and Eric Villa and Fidler, {Mary Kate} and Olmstead, {Marilyn M.} and Leone Spiccia and Britt, {R. David} and Casey, {William H.}",
doi = "10.1002/chem.201003550",
journal = "Chemistry - A European Journal",
T1 - Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution
AU - Ohlin, C. André
AU - Harley, Stephen J.
AU - McAlpin, J. Gregory
AU - Hocking, Rosalie K.
AU - Mercado, Brandon Q.
AU - Johnson, Rene L.
AU - Villa, Eric
AU - Fidler, Mary Kate
AU - Olmstead, Marilyn M.
AU - Spiccia, Leone
AU - Britt, R. David
AU - Casey, William H.
N2 - Polyoxometalate ions are used as ligands in water-oxidation processes related to solar energy production. An important step in these reactions is the association and dissociation of water from the catalytic sites, the rates of which are unknown. Here we report the exchange rates of water ligated to Co II atoms in two polyoxotungstate sandwich molecules using the 17O-NMR-based Swift-Connick method. The compounds were the [Co 4(H2O)2(B-α-PW9O 34)2]10- and the larger αββ α-[Co4(H2O)2(P2W 15O56)2]16- ions, each with two water molecules bound trans to one another in a CoII sandwich between the tungstate ligands. The clusters, in both solid and solution state, were characterized by a range of methods, including NMR, EPR, FT-IR, UV-Vis, and EXAFS spectroscopy, ESI-MS, single-crystal X-ray crystallography, and potentiometry. For [Co4(H2O)2(B-α-PW 9O34)2]10- at pH 5.4, we estimate: k298=1.5(5)±0.3à- 106 s-1, ΔH≠=39.8±0.4 kJmol-1, ΔS ≠=+7.1±1.2 Jmol-1K-1 and ΔV≠=5.6 ±1.6 cm3mol-1. For the Wells-Dawson sandwich cluster (αββα-[Co4(H 2O)2(P2W15O56) 2]16-) at pH 5.54, we find: k298=1.6(2) ±0.3à- 106 s-1, ΔH≠=27. 6±0.4 kJmol-1 ΔS≠=-33±1.3 Jmol -1K-1 and ΔV≠=2.2±1.4 cm 3mol-1 at pH 5.2. The molecules are clearly stable and monospecific in slightly acidic solutions, but dissociate in strongly acidic solutions. This dissociation is detectable by EPR spectroscopy as S=3/2 Co II species (such as the [Co(H2O)6]2+ monomer ion) and by the significant reduction of the Co-Co vector in the XAS spectra.
AB - Polyoxometalate ions are used as ligands in water-oxidation processes related to solar energy production. An important step in these reactions is the association and dissociation of water from the catalytic sites, the rates of which are unknown. Here we report the exchange rates of water ligated to Co II atoms in two polyoxotungstate sandwich molecules using the 17O-NMR-based Swift-Connick method. The compounds were the [Co 4(H2O)2(B-α-PW9O 34)2]10- and the larger αββ α-[Co4(H2O)2(P2W 15O56)2]16- ions, each with two water molecules bound trans to one another in a CoII sandwich between the tungstate ligands. The clusters, in both solid and solution state, were characterized by a range of methods, including NMR, EPR, FT-IR, UV-Vis, and EXAFS spectroscopy, ESI-MS, single-crystal X-ray crystallography, and potentiometry. For [Co4(H2O)2(B-α-PW 9O34)2]10- at pH 5.4, we estimate: k298=1.5(5)±0.3à- 106 s-1, ΔH≠=39.8±0.4 kJmol-1, ΔS ≠=+7.1±1.2 Jmol-1K-1 and ΔV≠=5.6 ±1.6 cm3mol-1. For the Wells-Dawson sandwich cluster (αββα-[Co4(H 2O)2(P2W15O56) 2]16-) at pH 5.54, we find: k298=1.6(2) ±0.3à- 106 s-1, ΔH≠=27. 6±0.4 kJmol-1 ΔS≠=-33±1.3 Jmol -1K-1 and ΔV≠=2.2±1.4 cm 3mol-1 at pH 5.2. The molecules are clearly stable and monospecific in slightly acidic solutions, but dissociate in strongly acidic solutions. This dissociation is detectable by EPR spectroscopy as S=3/2 Co II species (such as the [Co(H2O)6]2+ monomer ion) and by the significant reduction of the Co-Co vector in the XAS spectra.
U2 - 10.1002/chem.201003550
DO - 10.1002/chem.201003550
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
10.1002/chem.201003550