C–N Coupling in N₂ Fixation by the Ditantalum Carbide Cluster Anions Ta₂C₄^–

Abstract

The construction of C–N bonds by the direct incorporation of dinitrogen (N2) instead of ammonia (NH3) into active species is particularly desirable but has been rarely reported. Herein, a ditantalum carbide cluster anion (Ta2C4 –) capable of cleaving the NN bond and constructing a C–N bond under mild conditions has been identified using mass spectrometry, photoelectron imaging spectroscopy, and quantum-chemical calculations. The photoelectron spectrum of Ta2C4N2 – is remarkably different from that of Ta2C4 – and matches the simulated spectrum of the Ta2C4N2 – species with an end-on-bonded CN unit. The formation of the C–N bond has also been supported by the CN– fragment observed in the collision-induced dissociation of Ta2C4N2 –. The exceptional reactivity of Ta2C4 – is ascribed to the low-valent metal center serving as an electron reservoir. This study provides a non-NH3 route to construct C–N bonds by incorporating N2 into carbide compounds to produce nitrogenous species.

Direct transformation of dinitrogen: synthesis of N-containing organic compounds via N−C bond formation

“…Stimulated by the previous works on multinuclear Ti, Fe complexes-promoted N 2 cleavage and N−C bond formation [ 66 , 68 ], the strategy to realize synergistic N 2 -splitting and subsequent functionalization using polynuclear metal complexes should be further explored. Additionally, recent reports on gas-phase polynuclear metal clusters-mediated N 2 scission and subsequent N−C bond formation deserve further attention [ 79 , 80 ].…”

Side‐on‐End‐on Coordination of Dinitrogen on a Polynuclear Vanadium Nitride Cluster Anion [V5N5]−

“…The importance of the filled metal d orbitals with a proper symmetry (d xz or d yz ) has been emphasized . In sharp contrast, no experiment has been reported to capture the side‐on‐end‐on coordinated N 2 on gas‐phase species and such coordination was only predicted as transient (and very unstable) states during the process of N≡N cleavage . In this study, the 4 7‐1 species with the side‐on‐end‐on coordinated N 2 molecule is rather stable as it has a large binding energy of 1.95 eV ( 4 7‐1 ), which is much larger than that of the end‐on mode ( 4 7‐3 , 0.87 eV) and comparable to the dissociative adsorption product ( 4 7’‐1 , 2.23 eV).…”

“…The pseudo‐first‐order rate constant ( k 1 ) for the reaction of [V 5 14 N 5 ] − with 14 N 2 was determined to be (7±2)×10 −11 cm 3 molecule −1 s −1 , corresponding to the reaction efficiency of (12±3) % relative to the theoretical collision rate (Figure S1). The rate constant of the [V 5 N 5 ] − anion with N 2 is much faster than those of the related compound anions, for example, the rate constants of [Ta 2 C 4 ] − and [Ta 3 N 3 H] − with N 2 are 2×10 −11 and 3×10 −12 cm 3 molecule −1 s −1 , respectively . The relatively high value of k 1 ([V 5 N 5 ] − +N 2 ) implies a unique adsorption state of N 2 on [V 5 N 5 ] − .…”

Exploring Trimetallic Clusters Containing Alkali and Alkaline Earth Metal Atoms with High Activity for Nitrogen Activation

“…Gas-phase clusters are ideal models for simulating the active sites of related condensed phase systems, which can be used to understand the bond activation process under isolated and well-controlled conditions at a strictly molecular level [25][26][27][28], and is suitable to provide insights into the mechanisms of SAC and SCC [29]. A large number of experiments and theoretical work have explored the mechanism of N 2 activation by gas-phase clusters, mainly focusing on metal clusters [30][31][32][33][34][35], metal carbide clusters [36,37], and metal nitride clusters [38,39]. Coordination modes of N 2 on supporting atoms were found critical for N 2 activation.…”

“…Coordination modes of N 2 on supporting atoms were found critical for N 2 activation. On bimetallic clusters, N 2 can rst obtain the adsorption intermediate of side-on:end-on and then dissociate [35,37], or it can pass through the intermediate of side-on:side-on and then dissociate [40][41][42]. On trimetallic clusters, N 2 is adsorbed on the center of the metal triangle in the form of end-on:side-on:side-on or end-on:end-on:side-on coordination modes before dissociation [43][44][45][46].…”