Polarity-Inverted Nitrogen: Construction of Reactive Multiply-Bonded Functional Groups and Their Utilization

Objectif

With N-VERT, I introduce a broad-ranging concept to incorporate polarity-inverted nitrogen fragments in elusive multiple-bonded structures. Controlling bonding-interactions of nitrogen is a key societal enterprise, with ammonia fixation alone consuming 1-2% of the World’s annual energy output. Whereas classic reactions of nitrogen are generally dictated by its high electronegativity and strong triple bond, I propose to construct nitrogen-based multiple bonds using a class of metal scaffolds where nitrogen carries a lonepair of electrons but, nonetheless, exhibits inverted polarity. This unusual situation primes nitrogen for attack by electron-rich groups to form unsaturated motifs. Simultaneously, adaptive metal-nitrogen covalency leads to a reducing metal node, stabilizing sought motifs by backdonation. This concept could tame reactive multiple bonds, only suggested as fleeting intermediates. In main-group chemistry, stable triple bonds nearly only form between 2p elements, whereas heavier elements exhibit exceptionally weak bonding. We will insert an N atom into heavy-atom analogs of cyanide, dinitrogen and nitrosyl to probe their chemistry for the first time. We will also stabilize a hitherto unknown diazo compound and cast light on its dichotomous bonding. In addition, our bond-forming strategy may drive paradoxical reaction pathways, accumulating enthalpic potential in metastable bonds. These objectives branch out into divergent horizons; from fundamental main-group multiple bonds and aromaticity to organic single carbon-atom transfer and energy storage. The recent track-record of my group indicates viability of our strategy to isolate reactive intermediates far beyond the state-of-the-art. Addressing basic physicochemical properties of nitrogen, N-VERT is a groundbreaking, bottom-up approach to couple seemingly incompatible groups (archetypal nucleophiles) into elusive multiple-bonds; the studies have broad and fundamental impact on chemical synthesis.