Incorporation of Hydrogen‐Bonding Functionalities into the Second Coordination Sphere of Iron‐Based Water‐Oxidation Catalysts

Abstract

Through isoelectronic replacement of the oxygen atoms in SO42− ions by one CH2 and three NtBu groups one arrives formally at the dianion H2CS(NtBu)32−, which has been isolated for the first time in the form of the sulfur(VI) ylide complex [(tmeda)2Li2{CH2S(NtBu)3}] (see structure). Deprotonation of the S‐bonded methyl group in the triimidosulfonate MeS(NtBu)3− ion provides facile access in good yields. Hydrolysis favors the formation of the triimidosulfate [{(tmeda)Li2[OS(NtBu)3]}3] and methane, and not, as one might expect, diimidomethylenesulfate and the amine. tmeda=Me2NCH2CH2NMe2.

Evidence for an oxygen evolving iron–oxo–cerium intermediate in iron-catalysed water oxidation

“…Some of these species have also shown a remarkable competence towards water oxidation to form dioxygen, a reaction that involves O-O bond formation 4–7 . The reaction is particularly appealing because it has been recognized as one of the bottleneck challenges for the success of artificial photosynthesis, and the identification of iron compounds as efficient catalysts opens novel directions in the quest for earth-abundant systems that could be used on a large scale 8–11 .…”

Molecular Catalysts for Water Oxidation

“…Meyer's group also examined one iron complex in an electrochemically driven system. 318 Yang and co-workers 319 looked into the effect of introducing hydrogen-bonding proton acceptors adjacent to the presumed oxo-binding site in tetraaza Fe complexes. Trials were run with Chem.…”

Unraveling the Mechanism of Water Oxidation Catalyzed by Nonheme Iron Complexes

“…[35][36][37][38] As a result, major efforts have been devoted into experimental and theoretical mechanistic studies of homogeneous systems based on first row transition metals such as manganese, [39][40][41] and cobalt, [36,[42][43][44][45] and iron. [2,[46][47][48][49][50] Water oxidation catalysts (WOC) described so far may be classified in two main mechanisms: 1) A Lewis acid/base reaction by a nucleophilic attack of a water molecule (WNA; or a hydroxide) to a electrophilic metal-oxo center generating a hydroperoxo species, and [31] 2) a direct coupling mechanism (DC) through the interaction of two metal-oxo groups bearing a radical character, forming a peroxo intermediate. [51] Understanding of the mech-anisms responsible for the WO is a key issue to improve catalysts.…”