Heterobimetallic-Mediated Dinitrogen Functionalization: N-C Bond Formation at Rhenium-Group 9 Diazenido Complexes.

Abstract

We report the synthesis and characterization of rhenium-group 9 heterobimetallic diazenido species (η5-Cp)Re(μ-BDI)(μ-N2)M(η4-COD) (1-M, M = Ir or Rh, Cp = cyclopentadienide, BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate, COD = 1,5-cyclooctadiene), formed from salt elimination reactions between Na[(η5-Cp)Re(BDI)] and [MCl(η4-COD)]2. Additionally, we find that these same reagents react under an argon atmosphere to instead produce bridging hydride complexes (BDI)Re(μ-η5:η1-C5H4)(μ-H)M(η4-COD) (2-M), which undergo rearrangements upon protonation to form the alternative bridging hydrides [(η5-Cp)Re(μ-BDI)(μ-H)M(η4-COD)][(B(m-C6H3(CF3)2)4)] (3-M). Further, we demonstrate the first example of N-C bond formation at a heterobimetallic dinitrogen complex through reactions of 1-M and methyl triflate, which produces the alkylated species [(η5-Cp)Re(μ-N(Me)N)(μ-BDI)M(η4-COD)][OTf] (4-M, OTf = trifluoromethanesulfonate). A combination of spectroscopic studies, X-ray structural analysis, and computational investigations is discussed as an aid to understanding the modes of dinitrogen activation within these unique heterobimetallic complexes.