Isolation, Characterisation and Reactivity of N-Heterocyclic Diazoolefins

Examples for applications of nitrous oxide in organic synthesis remain rare up until today. First mayor contributions of our group were published in 2012, when nitrous oxide was successfully captured by N-heterocyclic carbenes. Subsequent studies investigated the bonding situation of nitrous oxide within these new molecules, shed light on their reactivity, and lead to the discovery of new routes for the synthesis of industrially important azoimidazolium dyes. This year, our group was able to demonstrate the use of azo dyes as mesoionic carbene ligands and as precursors for base induced dimerisations, which proceeded via a radical mechanism. Within the framework of my contribution to this work, I participated on the further project, then using the gained insights from that project for the development of organic super electron donors, unveiling an additional application of nitrous oxide to synthetic chemistry. During this research, we discovered another class of chemical compounds, which up to this moment was only theoretically described, but never successfully isolated and characterised. This new compound features a dinitrogen bound to a C=C unit, with the alpha carbon carrying a negative charge rather than a proton. We were able to show that these compounds don't display a linear C=C=N=N unit, but a bended geometry, as we successfully crystallised the first of these compounds several months ago. Now, we are pleased to report that these compounds were also classified as intermediates in the dimerisation, which we reported for our novel organic super electron donors. This finding not only helped us to understand the mechanism in our already submitted paper in precise detail, but also permitted a more lean synthesis of these donors, as water could be excluded easily from the reaction mixture - a challenge, which seemed elusive for the first attempts of synthesis, given that our organic super electron donor were made within a condensation reaction. Interestingly, an asymmetric dimerisation, a hetero-dimerisation, could be envisioned based upon our findings. Also, the synthesis of these unknown diazacumulenes was rather straight forward, only implying molecular sieves and carefully chosen conditions. A high yield of 75 % was reproducible. For the future, we are confident to predict miscellaneous applications for these diazacumulenes in synthesis. Leaving the field of water-free synthesis of difficult super electron donors, be it symmetric or asymmetric ones, we are eager to investigate on the opportunities these molecules carry in the area of metal-vinylidene complex synthesis. Also, dipolar cycloadditions should be possible to perform. All in all, diazacumulenes should have a bright future in synthetic organic and inorganic chemistry.