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

We report the synthesis and characterization of rhenium-group 9 heterobimetallic diazenido species (eta(5)-Cp)Re(mu-BDI)(mu-N-2)M(eta(4)-COD) (1-M, M = Ir or Rh, Cp = cyclopentadienide, BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-beta-diketiminate, COD = 1,5-cyclooctadiene), formed from salt elimination reactions between Na[(eta(5)-Cp)Re(BDI)] and [MCl(eta(4)-COD)](2). Additionally, we find that these same reagents react under an argon atmosphere to instead produce bridging hydride complexes (BDI)Re(mu-eta(5):eta(1)-C5H4)(mu-H)M(eta(4)-COD) (2-M), which undergo rearrangements upon protonation to form the alternative bridging hydrides [(eta(5)-Cp)Re(mu-BDI)(mu-H)M(eta(4)-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 [(eta(5)-Cp)Re(mu-N(Me)N)(mu-BDI)M(eta(4)-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.