Main-group element-mediated activation of dinitrogen

The prevalence of transition metals in dinitrogen activation is attributed to the fact that the unoccupied and occupied d orbitals could be both energetically and symmetrically accessible to accept electron density from and back donate to N2.

that the controllable, stepwise N2 activation by main group element began to thrive[editorializing], especially for those whose key intermediates were well structurally characterized and even isolated.

The single crystal X-ray analysis revealed a centrosymmetric dimer with terminal BDI ligands and side-on bridging N2 units.

The radical complex could be further reduced, forming the transient dicoordinate borylene species and thus had the ability to activate dinitrogen.

Following the further reduction by KC8 and stabilization by another borylene molecule, the dipotassium complex {[(CAAC)DurB]2(μ2-N2K2)} was formed in crystalline solid.

[4] Repeating the same reaction but replacing Dur (2,3,5,6-tetramethyl-phenyl) group by a bulkier Tip (2,4,6-triisopropylphenyl) group resulted in a very different result: after the dinitrogen was coordinated by the first borylene molecule, the second coordination by another borylene molecule was considerably hindered by steric repulsion in the case of the bulkier 4-Tip.

[5] Though key intermediate which activated N2 is unclear, DFT calculation suggested that the coordination of N2 occurs prior to the second chloride elimination.

Following the further reduction and coordination of boron, N2 was finally reduced to its lowest oxidation state and a mixture of two borylamine compounds, N(BCy2)3 and NH(BCy2)2, were generated.