Stabilization of Low-Valent Iron(I) in a High-Valent Vanadium(V) Oxide Cluster.

Low-valent iron centers are critical intermediates in chemical and bio-chemical processes. Herein, we show the first example of a low-valent Fe(I) center stabilized in a high-valent polyoxometalate framework. Electrochemical studies show that the Fe(III) -functionalized molecular vanadium(V) oxide (DMA)[Fe(III) ClV(V)12 O32 Cl](3-) (DMA=dimethylammonium) features two well-defined, reversible, iron-based electrochemical reductions which cleanly yield the Fe(I) species (DMA)[Fe(I) ClV(V)12 O32 Cl](5-) . Experimental and theoretical studies including electron paramagnetic resonance spectroscopy and density functional theory computations verify the formation of the Fe(I) species. The study presents the first example for the seemingly paradoxical embedding of low-valent metal species in high-valent metal oxide anions and opens new avenues for reductive electron transfer catalysis by polyoxometalates.