Abstract
Two new tetraphosphine ligands, P nC-PPh2 2N Ph 2 (1,5-diphenyl-3,7-bis((diphenylphosphino)alkyl)-1,5- diaza-3,7-diphosphacyclooctane; alkyl = (CH2)2, n = 2 (L2); (CH2)3, n = 3 (L3)), have been synthesized. Coordination of these ligands to cobalt affords the complexes [Co II(L2)(CH3CN)]2+ and [CoII(L3) (CH3CN)]2+, which are reduced by KC8 to afford [CoI(L2)(CH3CN)]+ and [CoI(L3) (CH3CN)]+. Protonation of the CoI complexes affords [HCoIII(L2)(CH3CN)]2+ and [HCo III(L3)(CH3CN)]2+. The cyclic voltammetry of [HCoIII(L2)(CH3CN)]2+, analyzed using digital simulation, is consistent with an ErCrEr reduction mechanism involving reversible acetonitrile dissociation from [HCoII(L2)(CH3CN)]+ and resulting in formation of HCoI(L2). Reduction of HCoIII also results in cleavage of the H-Co bond from HCoII or HCoI, leading to formation of the CoI complex [CoI(L2)(CH3CN)] +. Under voltammetric conditions, the reduced cobalt hydride reacts with a protic solvent impurity to generate H2 in a monometallic process involving two electrons per cobalt. In contrast, under bulk electrolysis conditions, H2 formation requires only one reducing equivalent per [HCoIII(L2)(CH3CN)]2+, indicating a bimetallic route wherein two cobalt hydride complexes react to form 2 equiv of [Co I(L2)(CH3CN)]+ and 1 equiv of H2. These results indicate that both HCoII and HCoI can be formed under electrocatalytic conditions and should be considered as potential catalytic intermediates.
| Original language | English |
|---|---|
| Pages (from-to) | 9975-9988 |
| Number of pages | 14 |
| Journal | Inorganic Chemistry |
| Volume | 52 |
| Issue number | 17 |
| DOIs | |
| Publication status | Published - Sep 2 2013 |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Physical and Theoretical Chemistry
Cite this
Synthesis and electrochemical studies of cobalt(III) monohydride complexes containing pendant amines. / Wiedner, Eric; Roberts, John; Dougherty, William G.; Kassel, W. Scott; DuBois, Daniel L; Bullock, R Morris.
In: Inorganic Chemistry, Vol. 52, No. 17, 02.09.2013, p. 9975-9988.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Synthesis and electrochemical studies of cobalt(III) monohydride complexes containing pendant amines
AU - Wiedner, Eric
AU - Roberts, John
AU - Dougherty, William G.
AU - Kassel, W. Scott
AU - DuBois, Daniel L
AU - Bullock, R Morris
PY - 2013/9/2
Y1 - 2013/9/2
N2 - Two new tetraphosphine ligands, P nC-PPh2 2N Ph 2 (1,5-diphenyl-3,7-bis((diphenylphosphino)alkyl)-1,5- diaza-3,7-diphosphacyclooctane; alkyl = (CH2)2, n = 2 (L2); (CH2)3, n = 3 (L3)), have been synthesized. Coordination of these ligands to cobalt affords the complexes [Co II(L2)(CH3CN)]2+ and [CoII(L3) (CH3CN)]2+, which are reduced by KC8 to afford [CoI(L2)(CH3CN)]+ and [CoI(L3) (CH3CN)]+. Protonation of the CoI complexes affords [HCoIII(L2)(CH3CN)]2+ and [HCo III(L3)(CH3CN)]2+. The cyclic voltammetry of [HCoIII(L2)(CH3CN)]2+, analyzed using digital simulation, is consistent with an ErCrEr reduction mechanism involving reversible acetonitrile dissociation from [HCoII(L2)(CH3CN)]+ and resulting in formation of HCoI(L2). Reduction of HCoIII also results in cleavage of the H-Co bond from HCoII or HCoI, leading to formation of the CoI complex [CoI(L2)(CH3CN)] +. Under voltammetric conditions, the reduced cobalt hydride reacts with a protic solvent impurity to generate H2 in a monometallic process involving two electrons per cobalt. In contrast, under bulk electrolysis conditions, H2 formation requires only one reducing equivalent per [HCoIII(L2)(CH3CN)]2+, indicating a bimetallic route wherein two cobalt hydride complexes react to form 2 equiv of [Co I(L2)(CH3CN)]+ and 1 equiv of H2. These results indicate that both HCoII and HCoI can be formed under electrocatalytic conditions and should be considered as potential catalytic intermediates.
AB - Two new tetraphosphine ligands, P nC-PPh2 2N Ph 2 (1,5-diphenyl-3,7-bis((diphenylphosphino)alkyl)-1,5- diaza-3,7-diphosphacyclooctane; alkyl = (CH2)2, n = 2 (L2); (CH2)3, n = 3 (L3)), have been synthesized. Coordination of these ligands to cobalt affords the complexes [Co II(L2)(CH3CN)]2+ and [CoII(L3) (CH3CN)]2+, which are reduced by KC8 to afford [CoI(L2)(CH3CN)]+ and [CoI(L3) (CH3CN)]+. Protonation of the CoI complexes affords [HCoIII(L2)(CH3CN)]2+ and [HCo III(L3)(CH3CN)]2+. The cyclic voltammetry of [HCoIII(L2)(CH3CN)]2+, analyzed using digital simulation, is consistent with an ErCrEr reduction mechanism involving reversible acetonitrile dissociation from [HCoII(L2)(CH3CN)]+ and resulting in formation of HCoI(L2). Reduction of HCoIII also results in cleavage of the H-Co bond from HCoII or HCoI, leading to formation of the CoI complex [CoI(L2)(CH3CN)] +. Under voltammetric conditions, the reduced cobalt hydride reacts with a protic solvent impurity to generate H2 in a monometallic process involving two electrons per cobalt. In contrast, under bulk electrolysis conditions, H2 formation requires only one reducing equivalent per [HCoIII(L2)(CH3CN)]2+, indicating a bimetallic route wherein two cobalt hydride complexes react to form 2 equiv of [Co I(L2)(CH3CN)]+ and 1 equiv of H2. These results indicate that both HCoII and HCoI can be formed under electrocatalytic conditions and should be considered as potential catalytic intermediates.
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U2 - 10.1021/ic401232g
DO - 10.1021/ic401232g
M3 - Article
VL - 52
SP - 9975
EP - 9988
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 17
ER -