Monomethylation and -protonation of Lutetium Dinitrogen Complex

Abstract

Due to the highly chemically inert nature, direct activation and transformation of dinitrogen are challenging. Here, we disclose the synthesis, isolation, and derivatization of (N 2 ) 3− supported by lutetium complex. Initially, a (N 2 ) 3− radical, in [{(C 5 Me 5 ){MeC(N i Pr) 2 }Lu} 2 (μ 2 -η 2 :η 2 -N 2 )][K(crypt)] (crypt = 2,2,2-cryptand) complex, was generated through the reduction of neutral lutetium dinitrogen complex [{(C 5 Me 5 ){MeC(N i Pr) 2 }Lu} 2 (μ 2 -η 2 :η 2 -N 2 )] with potassium metal. Subsequently, the reaction of (N 2 ) 3− complex with methyl triflate (or triflic acid) led to the formation of an N−C (or N−H) bond, yielding the corresponding [{(C 5 Me 5 ){MeC(N i Pr) 2 }Lu} 2 (NN-R)(OTf)][K(crypt)] (R = Me, H, OTf = CF 3 SO 3 ) 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.