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

Reduction of a tricobalt(II) tri(bromide) cluster supported by a tris(beta-diketiminate) cyclophane results in halide loss, ligand compression, and metal-metal bond formation to yield a 48-electron Co-3(I) cluster, Co3LEt/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 (mu(3)-eta(1):eta(2):eta(1)-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 N-2 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 N-2 scission with tris(trimethylsilyl)amine afforded in good yield.