Ammonia and Dinitrogen Activation by Surface Organometallic Chemistry on Silica‐Grafted Tantalum Hydrides

Abstract

(2b), accessed through surface organometallic chemistry (SOMC). The synthesis of the starting tantalum hydrides 2a and 2b by grafting tris(neopentyl)neopentylidenetantalum(V), Ta(=CH-tBu)Np 3 , on silica yields well-defined, isolated tantalum atoms. Silsesquioxane molecular modelling shows that the mechanism of the grafting reaction implies a tetraalkyl intermediate ]. The starting hydrides 2a and 2b react stoichiometrically and catalytically with alkanes in reactions such as alkane metathesis, cross-metathesis between ethane and toluene, and methane coupling to form ethane. Mechanistic

Cooperative Effect of Monopodal Silica-Supported Niobium Complex Pairs Enhancing Catalytic Cyclic Carbonate Production

“…of SiOH/mmol Nb), Et2O, rt, 20 h; iii) SiO2-200, (1 g), NbCl5•OEt2 (1.50 equiv. of Si-OH/mmol Nb), Et2O, rt, 20 h, see also 5 •OEt 2 on SiO 2-700 . Niobium pentachloride is known to be dimeric in the solid state via two bridging (µ 2 ) chlorine atoms; and the corresponding etherate complex has been shown to exist as monomeric NbCl 5 •OEt 2 .…”

C–H Bond Activation of Benzene, Toluene, 3,3‐Dimethyl‐1‐butene and Methane by Silica‐Supported TaV Imido Amido Surface Complex

“…A band centered at 2960 cm –1 , due to aliphatic hydrocarbons, is also observed in the gas phase IR spectrum. This observation could be compatible with the participation of the generally spectator13–15 surface neopentyl ligands (ν (CH) = 2960 cm –1 for (CH 3 ) 4 C (g) ), or some concomitant catalytic hydrogenation by the system. Efforts are ongoing to study this aspect. …”

“…IR Monitoring of the H/D Exchange of [(≡SiO) 2 Ta‐(=ND)(ND 2 )], 2‐d, with (CH 3 ) 3 C‐CH=CH 2 : A disk of 2‐d was prepared as described in the literature from ND 3 reaction with silica‐supported tantalum hydrides 1a and 1b 14–15. The vapor pressure of 3,3‐dimethyl‐1‐butene (350 Torr; 10 equiv./Ta) was added to the cell containing complex 2 at room temperature then heated at 150 °C overnight.…”

Molecular Pnictogen Activation by Rare Earth and Actinide Complexes

“…There are reviews on transition metal N2 activation which cover N2 binding modes [27][28][29], multimetallic N2 activation [30,31], the relevance of metal hydride complexes to N2 activation [32,33], N2 cleavage and functionalisation [34,35] (including electrochemical [36] and photolytic N2 cleavage [37]), and N2 activation at bare metal atoms [38] and using surface organometallic chemistry [39]. Specific reviews have also focused on activation by group 4 metals [40][41][42], iron [31,43,44], molybdenum [24,[45][46][47], and the mid-to-late transition metal centres [48].…”