Synthesis and Characterization of Bridging-Diazene Diiron Half-Sandwich Complexes: The Role of Sulfur Hydrogen Bonding.

We report two bridging-diazene diiron complexes Cp*Fe(8-quinolinethiolate) () and Cp*Fe(1,2-CyPCHS) (), synthesized by the reaction of hydrazine with the corresponding thiolate-based iron half-sandwich complex, [CpFe(8-quinolinethiolate)] () and CpFe(1,2-CyPCHS) (). Crystallographic analysis reveals that the thiolate sites in and can engage in N-H···S hydrogen bonding with the diazene protons. is thermally stable in both solid and solution states, allowing for one-electron oxidation to afford a cationic diazene radical complex [] at room temperature. In contrast, tends to undergo NH/N transformation, leading to the formation of a Fe(III)-H species by the loss of N. In addition to stabilizing HN=NH species through the hydrogen bonding, the thiolate-based ligands also seem to facilitate proton-coupled electron transfer, thereby promoting N-H cleavage.