The Cobalt Hydride that Never Was: Revisiting Schrauzer's "Hydridocobaloxime"
Abstract
Molecular cobalt-dmg (dmg = dimethylglyoxime) complexes are an important class of electrocatalysts used heavily in mechanistic model studies of the hydrogen evolution reaction (HER). Schrauzer's early isolation of a phosphine-stabilized "[H-Co^(III)(dmgH)_2P(nBu)_3]" complex has long provided circumstantial support for the plausible intermediacy of Co(III)-H species in HER by cobaloximes in solution. Our investigation of this complex has led to a reassignment of its structure as [Co^(II)(dmgH)_2P(nBu)_3], a complex that contains no hydride ligand and dimerizes to form an unsupported Co–Co bond in the solid state. A paramagnetic S = 3/2 impurity that forms during the synthesis of [Co^(II)(dmgH)_2P(nBu)_3] when exposed to adventitious oxygen has also been characterized. This impurity features a 1H NMR resonance at −5.06 ppm that was recently but erroneously attributed to the hydride resonance of "[H-Co^(III)(dmgH)_2P(nBu)_3]". We draw attention to this reassignment because of its relevance to cobaloxime hydrides and HER catalysis and because Schrauzer's "hydridocobaloxime" is often cited as the primary example of a bona fide hydride that can be isolated and characterized on this widely studied HER platform.
Additional Information
© 2015 American Chemical Society. Received: February 18, 2015; published: March 23, 2015. This work was supported by NSF Center for Chemical Innovation Solar Fuels Grant CHE-1305124. Larry Henling and Dr. Michael K. Takase are thanked for their help with X-ray crystallography. Sidney E. Creutz is thanked for assistance with SQUID measurements. D.C.L. would like to acknowledge the National Institute of Health (award number F32GM106726). G.M.R. would like to acknowledge the Peter A. Lindstrom, Jr. SURF fellowship.Attached Files
Supplemental Material - ja5b01838_si_001.pdf
Supplemental Material - ja5b01838_si_002.cif
Files
Name | Size | Download all |
---|---|---|
md5:6f738bd537b9cd11490549ca84e5a646
|
2.1 MB | Preview Download |
md5:ac93a9e4201ec9a82c2e1628ad42c22a
|
6.7 MB | Download |
Additional details
- Eprint ID
- 57773
- Resolver ID
- CaltechAUTHORS:20150522-100123322
- NSF
- CHE-1305124
- NIH
- F32GM106726
- Peter A. Lindstrom, Jr. SURF fellowship
- Caltech Summer Undergraduate Research Fellowship (SURF)
- Created
-
2015-05-22Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field