ic9b03633_si_001.pdf (1.58 MB)
O2 Activation by Non-Heme Thiolate-Based Dinuclear Fe Complexes
journal contribution
posted on 2020-02-14, 15:07 authored by Lianke Wang, Marcello Gennari, Fabián G. Cantú Reinhard, Sandeep K. Padamati, Christian Philouze, David Flot, Serhiy Demeshko, Wesley R. Browne, Franc Meyer, Sam P. de Visser, Carole DubocIron centers featuring
thiolates in their metal coordination sphere
(as ligands or substrates) are well-known to activate dioxygen. Both
heme and non-heme centers that contain iron-thiolate bonds are found
in nature. Investigating the ability of iron–thiolate model
complexes to activate O2 is expected to improve the understanding
of the key factors that direct reactivity to either iron or sulfur.
We report here the structural and redox properties of a thiolate-based
dinuclear Fe complex, [FeII2(LS)2] (LS2– = 2,2′-(2,2′-bipyridine-6,6′-iyl)bis(1,1-diphenylethanethiolate)),
and its reactivity with dioxygen, in comparison with its previously
reported protonated counterpart, [FeII2(LS)(LSH)]+. When reaction with O2 occurs in the absence of
protons or in the presence of 1 equiv of proton (i.e., from [FeII2(LS)(LSH)]+), unsupported μ-oxo
or μ-hydroxo FeIII dinuclear complexes ([FeIII2(LS)2O] and [FeIII2(LS)2(OH)]+, respectively) are generated. [FeIII2(LS)2O], reported previously but isolated
here for the first time from O2 activation, is characterized
by single crystal X-ray diffraction and Mössbauer, resonance
Raman, and NMR spectroscopies. The addition of protons leads to the
release of water and the generation of a mixture of two Fe-based “oxygen-free”
species. Density functional theory calculations provide insight into
the formation of the μ-oxo or μ-hydroxo FeIII dimers, suggesting that a dinuclear μ-peroxo FeIII intermediate is key to reactivity, and the structure of which changes
as a function of protonation state. Compared to previously reported
Mn–thiolate analogues, the evolution of the peroxo intermediates
to the final products is different and involves a comproportionation
vs a dismutation process for the Mn and Fe derivate, respectively.