Understanding the Role of Hyponitrite in Nitric Oxide Reduction

Abstract

Herein, we review the preparation and coordination chemistry of the cis and trans isomers of hyponitrite, [N 2 O 2 ] 2-. Hyponitrite is known to bind to metals via a variety of bonding modes. In fact, at least eight different bonding modes have been observed, which is remarkable for such a simple ligand. More importantly, it is apparent that the cis isomer of hyponitrite is more reactive than the trans isomer, as the barrier of N 2 O elimination from cis-hyponitrite is lower than that of trans-hyponitrite. This observation may have important mechanistic implications for both heterogeneous NO x reduction catalysts and NO Reductase. However, our understanding of the hyponitrite ligand has been limited by the lack of a general route to this fragment, and most instances of its formation have been serendipitous.3

HN2O2− as a Ligand in Mononuclear Hydrogenhyponitrite‐κ2‐N,O Ruthenium Complexes with Bisphosphane Co‐Ligands

“…Scheme2 highlights the factt hat hyponitritei sd iscussed not only as an intermediate in the enzymatic process of NOR, but is also al igand of currenti nterest in other fields of coordination chemistry.H ence, nine coordination modes are known for the hyponitrito ligand in its cis or trans forms. [11,12] Mononuclear complexes are restricted to the cis type whereby both isomersa re foundi np olynuclear complexes. Hyponitrite is able to bind up to four metal centers through each of its atoms.…”

“…Isolated deprotonated analogs are [Ru(dppe) 2 (N 2 O 2 )]·HImi(BF 4 )( 8)a nd [Ru(dppv) 2 (N 2 O 2 )] ·HImi(BF 4 )·Imi (10).Scheme1.Proposed mechanisms of hyponitrite formation. [11] [a]…”

Synthesis of a “Masked” Terminal Nickel(II) Sulfide by Reductive Deprotection and its Reaction with Nitrous Oxide

“…], [40] respectively,o r the reaction of N 2 Owith Na 2 O, which results in the formation of trans-[Na 2 N 2 O 2 ]. [41,42] Also relevant is the reaction of IPr with N 2 Ot of orm IPr-N 2 O. [43] These results support the conclusion that the [SN = NO] 2À ligand is formed by nucleophilic attack of N 2 Oa tt he sulfide ligand in 4.…”

A bridged di-iron porphyrin hyponitrite complex as a model for biological N2O production from hyponitrite

“…It is interesting to note that although hyponitrite complexes of coordination compounds are known [12,13], only two heme model-hyponitrite compounds have been reported to date [14,15], and only one has been structurally characterized. The first isolated hyponitrite-bridged iron heme model complex [(OEP)Fe] 2 ( 2 , 1 , 1 -ONNO) was reported by us [14].…”