10.1021/jo4028243.s001
Michal Szostak
Michal
Szostak
Malcolm Spain
Malcolm
Spain
David J. Procter
David J.
Procter
Determination of the Effective
Redox Potentials of
SmI<sub>2</sub>, SmBr<sub>2</sub>, SmCl<sub>2</sub>, and their Complexes
with Water by Reduction of Aromatic Hydrocarbons. Reduction of Anthracene
and Stilbene by Samarium(II) Iodide–Water Complex
American Chemical Society
2015
vs
electron transfer reactions
SmI 2 increases
2O
reduction potentials
SCE
redox
electron transfer reductants
Effective Redox Potentials
complex
mediates Birch reductions
2015-12-17 01:09:19
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Determination_of_the_Effective_Redox_Potentials_of_SmI_sub_2_sub_SmBr_sub_2_sub_SmCl_sub_2_sub_and_their_Complexes_with_Water_by_Reduction_of_Aromatic_Hydrocarbons_Reduction_of_Anthracene_and_Stilbene_by_Samarium_II_Iodide_Water_Complex/2030331
Samarium(II) iodide–water
complexes are ideally suited to
mediate challenging electron transfer reactions, yet the effective
redox potential of these powerful reductants has not been determined.
Herein, we report an examination of the reactivity of SmI<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> with a series of unsaturated
hydrocarbons and alkyl halides with reduction potentials ranging from
−1.6 to −3.4 V vs SCE. We found that SmI<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> reacts with substrates
that have reduction potentials more positive than −2.21 V vs
SCE, which is much higher than the thermodynamic redox potential of
SmI<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> determined
by electrochemical methods (up to −1.3 V vs SCE). Determination
of the effective redox potential demonstrates that coordination of
water to SmI<sub>2</sub> increases the effective reducing power of
Sm(II) by more than 0.4 V. We demonstrate that complexes of SmI<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> arising from
the addition of large amounts of H<sub>2</sub>O (500 equiv) are much
less reactive toward reduction of aromatic hydrocarbons than complexes
of SmI<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> prepared
using 50 equiv of H<sub>2</sub>O. We also report that SmI<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> cleanly mediates Birch
reductions of substrates bearing at least two aromatic rings in excellent
yields, at room temperature, under very mild reaction conditions,
and with selectivity that is not attainable by other single electron
transfer reductants.