Photochemically induced reductive elimination as a route to a zirconocene complex with a strongly activated N₂ ligand

The zirconocene dinitrogen complex [{(η(5)-C5Me4H)2Zr}2(μ2,η(2),η(2)-N2)] was synthesized by photochemical reductive elimination from the corresponding zirconium bis(aryl) or aryl hydride complexes, providing a high-yielding, alkali metal-free route to strongly activated early-metal N2 complexes. Mechanistic studies support the intermediacy of zirconocene arene complexes that in the absence of sufficient dinitrogen promote C-H activation or undergo comproportion to formally Zr(III) complexes. When N2 is in excess arene displacement gives rise to strong dinitrogen activation.