Dinitrogen Insertion and Cleavage by a Metal–Metal Bonded Tricobalt(I) Cluster

Reduction of a tricobalt­(II) tri­(bromide) cluster supported by a tris­(β-diketiminate) cyclophane results in halide loss, ligand compression, and metal–metal bond formation to yield a 48-electron Co^I₃ cluster, Co₃L^Et/Me (2). Upon reaction of 2 with dinitrogen, all metal–metal bonds are broken, steric conflicts are relaxed, and dinitrogen is incorporated within the internal cavity to yield a formally (μ₃-η¹:η²:η¹-dinitrogen)­tricobalt­(I) complex, 3. Broken symmetry DFT calculations (PBE0/def2-tzvp/D3) support an N–N bond order of 2.1 in the bound N₂ with the calculated N–N stretching frequency (1743 cm^–1) comparable to the experimental value (1752 cm^–1). Reduction of 3 under Ar in the presence of Me₃SiBr results in N₂ scission with tris­(trimethylsilyl)­amine afforded in good yield.