Monomethylation and -protonation of Lutetium Dinitrogen Complex

Due to the highly chemically inert nature, direct activation and transformation of dinitrogen are challenging. Here, we disclose the synthesis, isolation, and derivatization of (N₂)^3- supported by lutetium complex. Initially, a (N₂)^3- radical, in [{(C₅Me₅){MeC(NⁱPr)₂}Lu}₂(μ²-η²:η²-N₂)][K(crypt)] (crypt = 2,2,2-cryptand) complex, was generated through the reduction of neutral lutetium dinitrogen complex [{(C₅Me₅){MeC(NⁱPr)₂}Lu}₂(μ²-η²:η²-N₂)] with potassium metal. Subsequently, the reaction of (N₂)^3- complex with methyl triflate (or triflic acid) led to the formation of an N-C (or N-H) bond, yielding the corresponding [{(C₅Me₅){MeC(NⁱPr)₂}Lu}₂(NN-R)(OTf)][K(crypt)] (R = Me, H, OTf = CF₃SO₃) as the product. Both electron paramagnetic resonance spectroscopy and density functional theory analyses support the radical character of the NN-Me unit. The Lu-N bonds in the (NN-Me)^•2- radical complex are predominantly ionic, with 77% of the unpaired electron localized on the (NN-Me) fragment. Moreover, the geometry of the pure organic radical (NN-Me)^•2-, optimized by double-hybrid density functional theory, closely matches that of the (NN-Me)^•2- lutetium complex.