Synthesis, Reactivity, and Electronic Structure of a Bioinspired Heterobimetallic [Ni(μ‑S2)Fe] Complex with Disulfur Monoradical character
dataset
posted on 2014-06-23, 00:00 authored by Robert Rudolph, Burgert Blom, Shenglai Yao, Florian Meier, Eckhard Bill, Maurice van Gastel, Nils Lindenmaier, Martin Kaupp, Matthias DriessThe
first synthesis of a monoradical Ni(μ-S2)Fe
core in the [(Nacnac)Ni(μ-S2)Fe(dmpe)2] complex 3 could be accomplished in good yields by
PMe3 elimination from the zerovalent iron complex [(dmpe)2(PMe3)Fe] (2; dmpe =1,2-bis(dimethylphosphine)ethane)
upon reaction with the supersulfido nickel(II) complex [(Nacnac)Ni(S2)] (1; Nacnac = CH{(CMe)(2,6-iPr2C6H3N)}2). Complex 3 bears Ni(II) and Fe(II) centers, both of which are in a
low-spin state. A single electron is located in the HOMO and is somewhat
delocalized over the Ni(μ-S2)Fe core, so that the
bridging disulfur subunit exhibits some “subsulfide”
S23– character. Compound 3 represents a bioinspired example of a monoradical with a Ni(μ-S2)Fe structural motif, reminiscent of the Ni(μ-S2)Fe core structure of the active site in [NiFe] hydrogenases.
Its oxidation with [Fe(η5-C5H5)2][B(C6H3(CF3)2)4] affords the product [(Nacnac)Ni(μ-S)2Fe(dmpe)2][B(C6H3(CF3)2)4] (4), and complex 3 can alternatively be prepared via a reductive route upon reaction
of [Co(η5-C5Me5)2][(Nacnac)NiS2] (6) with the Fe(0) precursor 2. All synthesized complexes were fully characterized, including
in some cases single-crystal X-ray diffraction analysis, magnetometry,
EPR, NMR, and 57Fe Mössbauer spectroscopy. DFT calculations
were used to compute the spectroscopic parameters and to establish
the electronic structure of 3 and its oxidized and reduced
forms and related complexes.
