Six-Membered Iridacycles with Five Nitrogen Atoms in the Ring

Catalytic diazene metathesis is a fundamental inorganic transformation that remains unrealized despite its potential value, given the photochemical properties of the diazene functional group. Diazenes and polymers comprising them have a multitude of functions ranging from molecular motors to dyes and actuators, and catalytic diazene metathesis would be an enabling tool for their synthesis. However, current approaches to diazene metathesis founded on the [2+2] cycloaddition/elimination mechanism have not been able to achieve catalyst turnover. Alternative mechanisms for this metathesis based on insertion/elimination could circumvent this challenge. As a crucial step toward realizing this mechanism, we have synthesized several complexes that resemble potential intermediates in a proposed insertion/elimination mechanism for diazene metathesis: specifically, these complexes feature six-membered metallocycles comprising one iridium and five contiguous nitrogen atoms. These complexes can be prepared in a straightforward manner through the reaction of N-alkyl triazoline diones with an iridium imido complex within minutes at room temperature. Furthermore, redox reactivity of these complexes is explored leading to the formation of novel azo imides. This work provides an alternative starting point for mechanism and catalyst design toward catalytic diazene metathesis.