Isocyanide Substituent Influences Reductive Elimination\nversus Migratory Insertion in Reaction with an [Fe<sub>2</sub>(μ-H)<sub>2</sub>]<sup>2+</sup> Complex

Iron hydrides are proposed reactive\nintermediates for N<sub>2</sub> and CO conversion in industrial and\nbiological processes. Here,\nwe report a reactivity study of a low-coordinate di(μ-hydrido)diiron(II)\ncomplex, Fe<sub>2</sub>(μ-H)<sub>2</sub><b>L</b>, where <b>L</b><sup><b>2</b>–</sup> is a bis(β-diketiminate)\ncyclophane, with isocyanides, which have electronic structures related\nto N<sub>2</sub> and CO. The reaction outcome is influenced by the\nisocyanide substituent, with 2,6-xylyl isocyanide leading to H<sub>2</sub> loss, to form a bis(μ-1,1-isocyanide)diiron(I) complex,\nwhereas all of the other tested isocyanides insert into the Fe–H\nbond to give (μ-1,2-iminoformyl) complexes. Steric bulk of the\nisocyanide substituent determines the extent of insertion (i.e., into\none or both Fe–H–Fe units) with <i>tert</i>-butyl isocyanide reacting to yield the mono-(μ-1,2-iminoformyl)diiron(II)\ncomplex, exclusively, and isopropyl- and methyl isocyanides affording\nthe bis(μ-1,2-iminoformyl)diiron(II) products. Treatment of\nFe<sub>2</sub>(μ-1,2-CHNtBu)(μ-H)<b>L</b> with 2,6-xylyl\nisocyanide (or XylNC) yields Fe<sub>2</sub>(μ-XylNC)<sub>2</sub><b>L</b> and <i>tert</i>-butylaldimine as one of\nthe organic products.