Hydrogen Peroxide Coordination to Cobalt(II) Facilitated by Second‐Sphere Hydrogen Bonding

Abstract

M(H2 O2 ) adducts have been postulated as intermediates in biological and industrial processes; however, only one observable M(H2 O2 ) adduct has been reported, where M is redox-inactive zinc. Herein, direct solution-phase detection of an M(H2 O2 ) adduct with a redox-active metal, cobalt(II), is described. This Co(II) (H2 O2 ) compound is made observable by incorporating second-sphere hydrogen-bonding interactions between bound H2 O2 and the supporting ligand, a trianionic trisulfonamido ligand. Thermodynamics of H2 O2 binding and decay kinetics of the Co(II) (H2 O2 ) species are described, as well as the reaction of this Co(II) (H2 O2 ) species with Group 2 cations.

Intramolecular hydrogen-bonding in a cobalt aqua complex and electrochemical water oxidation activity

“… 6 , 7 , 26 , 52 – 57 Hydrogen-bond acceptors have also been shown to stabilize cobalt hydroxide or hydroperoxo ligands. 58 , 59 Our efforts to isolate or spectroscopically identify intermediates during water oxidation using stoichiometric chemical oxidants and bases were unsuccessful. However, the marked difference in water oxidation activity between 1 and 2 , along with the deuterium isotope effect, indicate the potential role of intramolecular proton acceptors in facilitating redox catalysis.…”

Effect of aluminum vacancies on the H2O2 or H2O interaction with a gamma‐AlOOH surface. A solid‐state DFT study

“…Furthermore, an understanding of how to facilitate formation of metal‐H 2 O 2 adducts opens a new pathway for exploring H 2 O 2 activation for substrate oxidation reactions, a goal that we are currently pursuing. It has been recently demonstrated that H 2 O 2 coordination with zinc and cobalt is facilitated by second‐sphere hydrogen‐bonding interactions with the two hydrogen bonds of the H 2 O 2 molecule as proton donor (DH‐bonds) . Formation of two relatively short (strong) DH‐bonds by H 2 O 2 molecule is always realized in peroxosolvates with organic and inorganic molecules and salts due to the relatively high acidity of the hydrogen peroxide .…”

“…Formation of two relatively short (strong) DH‐bonds by H 2 O 2 molecule is always realized in peroxosolvates with organic and inorganic molecules and salts due to the relatively high acidity of the hydrogen peroxide . It was suggested that hydrogen bonding of the metal coordinated hydrogen peroxide is a general phenomenon that plays a key role in the stabilization of the M–(H 2 O 2 ) complex.…”

Exploring secondary-sphere interactions in Fe–NxHycomplexes relevant to N2fixation

“…Whereas there has been sustained interest in modeling the structures and functions of metalloenzymes using synthetic, small-molecule systems, 1,2 models of metalloenzyme active sites that reproduce only the primary coordination sphere rarely capture the catalytic activity of interest. In the vast majority of cases, model complexes lack important peripheral secondary sphere interactions commonly present in biological systems.…”

“…In a number of cases, especially in the context of proton reduction and oxygen activation, these approaches have been notably successful, both with respect to engendering favorable catalytic reactivity and in stabilizing reactive species such as terminal metal oxos. 2 …”