A Triad of Highly Reduced, Linear Iron Nitrosyl Complexes: {FeNO}8–10. Issue 39 (25th August 2016) - Chalkley, Matthew J.
Abstract: Given the importance of Fe–NO complexes in both human biology and the global nitrogen cycle, there has been interest in understanding their diverse electronic structures. Herein a redox series of isolable iron nitrosyl complexes stabilized by a tris(phosphine)borane (TPB) ligand is described. These structurally characterized iron nitrosyl complexes reside in the following highly reduced Enemark–Feltham numbers: {FeNO} 8, {FeNO} 9, and {FeNO} 10 . These {FeNO} 8–10 compounds are each low‐spin, and feature linear yet strongly activated nitric oxide ligands. Use of Mössbauer, EPR, NMR, UV/Vis, and IR spectroscopy, in conjunction with DFT calculations, provides insight into the electronic structures of this uncommon redox series of iron nitrosyl complexes. In particular, the data collectively suggest that {TPBFeNO} 8–10 are all remarkably covalent. This covalency is likely responsible for the stability of this system across three highly reduced redox states that correlate with unusually high Enemark–Feltham numbers. Abstract : Linear alignment : Model iron nitrosyl complexes have been well‐studied due to their biological significance and interesting underlying electronic structures. However, species with high Enemark–Feltham numbers (8–10) remain rare. An unusual redox series of {FeNO} 8–10 complexes supported by a tris(phosphine)borane maintains a linear Fe‐N‐O angle throughout the series; the reasons for this atypical behavior have been investigated spectroscopically.