Examining the relationship between coordination mode and reactivity of dinitrogen

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Abstract

Molecular nitrogen (N2) is the most abundant gas in Earth's atmosphere, but its low reactivity has hampered its use as a precursor to higher value nitrogen-containing compounds. Coordination of N2 to metal centres offers a way to overcome this intrinsic inertness and allows the discovery of new transformations. The expanding family of isolable N2 coordination complexes exhibits various bonding modes that, in particular cases, facilitate catalytic or stoichiometric transformations of the N2 unit. In this Review, we survey metal complexes of N2 in order to correlate bonding mode with functionalization propensity. Although many factors influence the functionalization of N2, we propose that coordination mode could be more important than previously recognized.

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Figure 1: N2 coordinated in a terminal end-on manner is reactive towards acids and electrophiles.
Figure 2: Terminal end-on N2 complexes supported by N- and/or P-donor ligands as catalyst precursors for N2 reductions.
Figure 3: Reduction of bridging end-on N2 complexes to metal nitride species.
Figure 4: Catalytic ammonia production facilitated by a dimolybdenum complex bearing end-on bridging and terminal N2 ligands.
Figure 5: Complexes of bridging side-on N2 can afford various organic and organometallic products.
Figure 6: Dinuclear group 4 metal complexes of bridging side-on N2 undergo electrophilic attack to afford various N-containing products.
Figure 7: Complexes of side-on end-on N2 can be prepared through different routes and react with Lewis acids and unsaturates.

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Acknowledgements

The authors thank the Natural Sciences and Engineering Research Council of Canada (NSERC) for continued financial support.

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Correspondence to Michael D. Fryzuk.

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