Synthesis and Characterization of a Linear Dinitrosyl-Triiron Complex; Comparison to a Flavodiiron Nitric Oxide Reductase Intermediate

Abstract

Nitric oxide is released during the immune response by the host during bacterial infection. To counteract this response, bacteria have evolved nitric oxide reductases to convert NO to N[subscript 2]O. Some of these nitric oxide reductases contain a flavodiiron active site that has bridging carboxylates and hydroxides. Only a handful of synthetic complexes currently exist as models for the protein reactivity. Here, we report the reaction of [Fe[subscript 2](μ-OH)(μ-Ph[subscript 4]DBA)(TMEDA)[subscript 2](OTf)] (4) with NO(g) and Ph[subscript 3]CSNO to prepare the dinitrosyl-triiron complex [Fe[subscript 3](μ-OH)[subscript 2](μ-Ph[subscript 4]DBA)[subscript 2](TMEDA)[subscript 2](NO)[subscript 2]](OTf) (5). The reaction was monitored by UV/Vis and ReactIR spectroscopy, and compound 5 was characterized by X-ray crystallography, [superscript 57]Fe Mossbauer spectroscopy, Evan's method, and FTIR spectroscopy. The IR spectrum of compound 5 compares favorably to experimental spectroscopic data obtained for the proposed mononitrosylated intermediate of the protein.