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Updated: May 21, 2026

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Oxygen reduction reactions of monometallic rhodium hydride complexes
Thomas S Teets1, Daniel G Nocera
1Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States.
Abstract:
Selective reduction of oxygen is mediated by a series of monometallic rhodium(III) hydride complexes. Oxidative addition of HCl to trans-Rh(I)Cl(L)(PEt(3))(2) (1a, L = CO; 1b, L = 2,6-dimethylphenylisocyanide (CNXy); 1c, L = 1-adamantylisocyanide (CNAd)) produces the corresponding Rh(III) hydride complex cis-trans-Rh(III)Cl(2)H(L)(PEt(3))(2) (2a-c). The measured equilibrium constants for the HCl-addition reactions show a pronounced dependence on the identity of the "L" ligand. The hydride complexes effect the reduction of O(2) to water in the presence of HCl, generating trans-Rh(III)Cl(3)(L)(PEt(3))(2) (3a-c) as the metal-containing product. In the case of 2a, smooth conversion to 3a proceeds without spectroscopic evidence for an intermediate species. For 2b/c, an aqua intermediate, cis-trans-[Rh(III)(OH(2))Cl(2)(L)(PEt(3))(2)]Cl (5b/c), forms along the pathway to producing 3b/c as the final products. The aqua complexes were independently prepared by treating peroxo complexes trans-Rh(III)Cl(L)(η(2)-O(2))(PEt(3))(2) (4b/c) with HCl to rapidly produce a mixture of 5b/c and 3b/c. The reactivity of the peroxo species demonstrates that they are plausible intermediates in the O(2)-reduction chemistry of hydride complexes 2a-c. These results together show that monometallic rhodium hydride complexes are capable of promoting selective reduction of oxygen to water and that this reaction may be controlled with systematic alteration of the ancillary ligand set.
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