Dinitrogen Activation and Functionalization by Multimetallic Hydride Clusters

Abstract Multimetallic hydride clusters provide an excellent platform for the cooperative activation and transformation of small molecules under mild conditions. This account highlights our recent advances in the synthesis, reactivity, and mechanistic understanding of titanium-based hydride clusters capable of the cleavage and functionalization of N2. A trinuclear titanium heptahydride cluster exhibits remarkable reactivity, enabling stepwise N≡N bond reduction, cleavage, and hydrogenation without external reductants. Beyond N2 activation, the same cluster promotes unprecedented transformations of aromatic compounds, including C–C and C–N bond cleavage and carbon skeletal rearrangement of benzene and pyridines. Importantly, titanium hydride clusters mediate the direct hydroamination of simple alkenes with N2, affording alkylamines via C(sp2)–H and N–N bond cleavage followed by selective N–C bond formation. Expanded reactivity has further been realized using dititanium, chromium, and heterometallic hydride clusters, enabling N–X (X = H, B, Al, Si) bond formation, coupling reactions of N2 with α, β-unsaturated carbonyls or CO2, and N2 activation. Together, these findings establish multimetallic hydride frameworks as a promising platform for developing new molecular approaches to N2 fixation and the direct synthesis of value-added nitrogen-containing organic compounds.