One- vs Two-Electron Reduction of N2O Promoted by a Divalent Chromium Macrocyclic Complex

Reaction of [Cr(ORPG)Li2(THF)4] (1) [ORPG = octaalkylporphyrinogen R = Et (a), n-Pr (b)] with N2O gave two different products depending on the solvent employed. While a deoxygenation reaction was observed in toluene with formation of the Cr(IV) complex [(THF)(ORPG)Cr(O)(LiTHF)2] (2), reactions carried out in THF yielded a Cr(III) species [Cr(ORPG)(THF)2][Li(THF)4] (3) where only one electron was transferred to N2O. The structures of 1b, 2a, and 3a have been elucidated by X-ray crystal structures. Crystal data are as follows. 1b: C60H96O4CrN4Li2, monoclinic P21/c, a = 20.504(2) Å, b = 12.347(1) Å, c = 22.524(1) Å, β = 94.56(1)°, Z = 4. 2a: C48H72O4CrN4Li2, monoclinic P21/n, a = 11.687(1) Å, b = 20.273(3) Å, c = 19.467(3) Å, β = 100.27(1)°, Z = 4. 3a: C60H96O6CrN4Li, monoclinic P21/c, a = 13.884(1) Å, b = 16.170(1) Å, c = 25.514(2) Å, β = 90.59(1)°, Z = 4.