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Title: Synthesis and Electrochemical Studies of Cobalt(III) Monohydride Complexes Containing Pendant Amines

Two new tetraphosphine ligands, PnC-PPh 22NPh 2 (1,5-diphenyl-3,7-bis((diphenylphosphino)alkyl)-1,5-diaza-3,7-diphosphacyclooctane; alkyl = (CH 2) 2, n = 2 (L2); (CH 2) 3, n = 3 (L3)), have been synthesized. Coordination of these ligands to cobalt affords the complexes [CoII(L2)(CH 3CN)] 2+ and [CoII(L3)(CH 3CN)] 2+, which are reduced with KC8 to afford [CoI(L2)(CH 3CN)] 1+ and [CoI(L3)(CH 3CN)] 1+. Protonation of the CoI complexes affords [HCo III(L2)(CH 3CN)] 2+ and [HCo III(L3)(CH 3CN)] 2+. Reduction of HCo III results in formation of the analogous CoI complex through H-Co bond cleavage. Under voltammetric conditions, the reduced cobalt hydride reacts rapidly with a protic solvent impurity to generate H 2 in a monometallic process involving two electrons per cobalt. In contrast, under bulk electrolysis conditions, H 2 formation requires only one reducing equivalent per [HCo III(L2)(CH 3CN)] 2+, indicating a bimetallic route wherein two cobalt hydride complexes react to form two equiv [CoI(L2)(CH 3CN)] 1+ and one equiv H 2. The cyclic voltammetry of [HCo III(L2)(CH 3CN)] 2+, analyzed using digital simulation, is consistent with an ErCrEr reduction mechanism involving reversible acetonitrile dissociation from [HCo II(L2)(CH 3CN)] 1+. We thank the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences,more » Geosciences and Biosciences, for support of the initial parts of this study. Current work is supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less
 [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Villanova Univ., PA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0020-1669; KC0302010; KC0307010
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 52; Journal Issue: 17
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; cobalt; electrocatalysis; hydrogen production