NO Coupling by Nonclassical Dinuclear Dinitrosyliron Complexes to Form N₂O Dictated by Hemilability

Selective coupling of NO by a nonclassical dinuclear dinitrosyliron complex (D-DNIC) to form N 2 O is reported. The coupling is facilitated by the pyridinediimine (PDI) ligand scaffold, which enables the necessary denticity changes to produce mixed-valent, electron-deficient tethered DNICs. One-electron oxidation of the [{Fe(NO) 2 }] 2 10/10 complex Fe 2 ( Pyrr PDI)(NO) 4 ( 4 ) results in NO coupling to form N 2 O via the mixed-valent {[Fe(NO) 2 ] 2 } 9/10 species, which possesses an electron-deficient four-coordinate {Fe(NO) 2 } 10 site, crucial in N–N bond formation. The hemilability of the PDI scaffold dictates the selectivity in N–N bond formation because stabilization of the five-coordinate {Fe(NO) 2 } 9 site in the mixed-valent [{Fe(NO) 2 }] 2 9/10 species, [Fe 2 ( Pyr2 PDI)(NO) 4 ][PF 6 ] ( 6 ), does not result in an electron-deficient, four-coordinate {Fe(NO) 2 } 10 site, and hence no N–N coupling is observed.