Mechanistic Study of Hydroamination of Alkyne through Tantalum-Based Silica-Supported Surface Species

Aljuhani, Maha A.; Zhang, Ziyun; Barman, Samir; Eter, Mohamad El; Failvene, Laura; Ould‐Chikh, Samy; Guan, Erjia; Abou-Hamad, Edy; Emwas, Abdul‐Hamid; Pelletier, Jérémie D. A.; Gates, Bruce C.; Cavallo, Luigi; Basset, Jean‐Marie

doi:10.1021/acscatal.9b02184

Cited by 15 publications

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“…Therefore, in the present study, we have explored the possibility of grafting the homoleptic tetrakis(dimethylamido) complexes [Ti(NMe 2 ) 4 ] on highly dehydroxylated silica (SiO 2‑700 ), with the intent of drawing a full image of what was done previously in our group with the homoleptic zirconuim complex. − The objective was to isolate, using SOMC concepts and tools, − all or some of the elementary steps of the catalytic cycle of heterogeneous hydroaminoalkylation previously proposed in homogeneous catalysis. − …”

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confidence: 99%

Evidence for Silica Surface Three- and Five-Membered Metallacycle Intermediates in the Catalytic Cycle of Hydroaminoalkylation of Olefins Using Single-Ti-Metal Catalysts

et al. 2020

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The single-site silica-supported group IV metal amido complex [Ti(NMe 2 ) 4 ] gives the tris(amido)-supported fragment [(Si−O−)Ti(−NMe 2 ) 3 ], which transforms into a three-membered metallacycle (called a metallaaziridine) by an α-H transfer between two amido ligands. When the three-membered metallacycle reacts with 1-octene, it gives a five-membered metallacycle by insertion of the double bond into the M−C bond of the metallaziridine. These two metallacycles, key intermediates in the catalytic cycle of the hydroaminoalkylation of terminal olefins, were isolated and fully characterized following the surface organometallic chemistry (SOMC) concept and procedures. This paper shows that surface organometallic chemistry can be used to identify and fully characterize three-and five-membered metallacycles of Ti in the hydroaminoalkylation of olefins. Article pubs.acs.org/Organometallics

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confidence: 99%

Evidence for Silica Surface Three- and Five-Membered Metallacycle Intermediates in the Catalytic Cycle of Hydroaminoalkylation of Olefins Using Single-Ti-Metal Catalysts

et al. 2020

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“…The spinning frequency was set to 22 and 14 KHz for 1 H and 13 C spectra, respectively, and adamantine was used as an external reference for both 1 H at 1.77 ppm and 13 C at 37.77 ppm. For CP/MAS 13 C NMR, the following sequence was used: 90° pulse on the proton (pulse length = 2.4 s), then a cross-polarization step with a contact time of typically 2 ms, and finally the acquisition of the 13 C signal under conditions of high-power proton decoupling . The delay between the scan was set to 5 s to allow the complete relaxation of the 1 H and 13 C nuclei, and the scan relaxation delay was set to 2 s for the 27 Al nuclei; the number of scans was between 3000 and 25,000 for carbon, 128 for proton, and 10,485 for aluminum.…”

Section: Methodsmentioning

confidence: 99%

“…For CP/MAS 13 C NMR, the following sequence was used: 90°pulse on the proton (pulse length = 2.4 s), then a cross-polarization step with a contact time of typically 2 ms, and finally the acquisition of the 13 C signal under conditions of high-power proton decoupling. 64 The delay between the scan was set to 5 s to allow the complete relaxation of the 1 H and 13 C nuclei, and the scan relaxation delay was set to 2 s for the 27 Al nuclei; the number of scans was between 3000 and 25,000 for carbon, 128 for proton, and 10,485 for aluminum. An apodization function (exponential) corresponding to a line broadening of 50 Hz was applied prior to Fourier transformation.…”

Section: Preparation Of the Partially Dehydroxylated Mesoporous Zeoli...mentioning

confidence: 99%

Surface Organometallic Chemistry on Zeolites: Synthesis of Group IV Metal Alkyls and Metal Hydrides on Hierarchical Mesoporous H-ZSM-5

et al. 2022

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Surface organometallic chemistry (SOMC) has mainly been devoted to the reaction of organometallics with surfaces comprising highly divided and dehydroxylated oxides. The field has been extended to SOMC on metal nanoparticles. However, to the best of our knowledge, SOMC has not been extended to hierarchical fibrous zeolites, although zeolitic materials are a particular class of oxides. Zeolite catalysis is important in hydrocarbon industrial chemistry. However, having an optimum balance between the activity and selectivity of the zeolitic catalysts remains a major challenge in the field. The main difficultly is the plethora of surface sites, only some of which are catalytically active. Given that the acido–basic properties and porosity of zeolites are especially important to the refining and petrochemical industries, we decided to explore this rather unexplored area. Here, three novel well-defined single-site materials [(Np)3M@ZSM-5, M = Ti, Zr, and Hf] supported on a hierarchical mesoporous H-ZSM-5 material (1) are reported. They are prepared using the concepts and tools of SOMC. They are further converted to their corresponding metal hydride [(H) n M@ZSM-5, M = Ti, Zr, and Hf, (n = 1–2)] materials (5–7) through controlled hydrogenolysis of [(Si–O−)M(Np)3, M = Ti, Zr, and Hf] materials (2–4) under H2 (1 atm) at 150 °C for 16 h. All these surface catalysts are characterized by various spectroscopic techniques including Fourier transform infrared spectroscopy, elemental analysis, solid-state NMR spectroscopy, powder X-ray diffraction, Brunauer–Emmett–Teller surface area measurements, and scanning electron microscopy and high-resolution transmission electron microscopy analyses and are supported by density functional theory calculations. The catalytic activity of these well-defined single-site novel materials will be tested for the catalytic applications in petrochemistry for refinery processes such as hydrocracking of distillates from crude oil or intermediate refinery process streams to useful petroleum value-added products for the society.

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“…Silica-supported Ta catalysts have a higher activity than their homogeneous counterparts. The supported Ta catalysts were also active in the hydroamination , and H-D exchange reaction . Recently, other titanium imido complexes active in the heterometathesis reaction have been reported (Scheme ).…”

Section: Supported Metal Complexes Designed Through Somcmentioning

confidence: 99%

Enhanced Catalysis Based on the Surface Environment of the Silica-Supported Metal Complex

et al. 2021

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Silica-supported metal complex catalysts have been developed and used for organic transformations. The surface environment around the supported metal complex enhances the catalysis based on a unique surface effect. The design of the linker ligand structure induces the formation of a highly reactive, coordinatively unsaturated metal complex on the silica surface because of the isolated environment. In contrast to the site-isolation effect, the accumulated metal complexes and cocatalysts on the same surface facilitate the acceleration of the catalytic reaction by concerted catalysis. The immobilization of multiactive sites also promotes the tandem catalysis and development of complex products from simple molecules through successive reactions. Surface silanol species originating from the silica support also participate in the catalysis. The control of the immobilization density/location of metal complex/coimmobilized functionality/surface silanol is a key factor for the achievement of site-isolation/concerted catalysis. The direct interaction between the metal complex and coimmobilized functionality facilitates the formation of unique reactive species. The confinement effect of the pore structure of the support enhances the accumulation of active species in mesopores, which boosts the reaction rate, and slightly changes the ligand conformation, which increases the enantioselectivity. The direct support electronic effect is also one of the key factors affecting the surface organometallic chemistry (SOMC) and photooxidation of linker metal complexes. These acceleration effects were detected in both supported homogeneous catalysis and SOMC. Not only the local structure of the metal complex and its ligand but also the surface environment play the most important roles in enhancing the catalysis. In this Review, representative examples of silica-supported metal complexes whose catalysis is significantly enhanced by their surface long-range environment are summarized. The contributions of recent developments of spectroscopic techniques, including DNP-enhanced solid-state NMR and XAFS, which support the evaluation of such long-range interactions, are also discussed. The surface design of the silica-supported metal complex facilitates highly active, selective, and durable catalysis.

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Mechanistic Study of Hydroamination of Alkyne through Tantalum-Based Silica-Supported Surface Species

Abstract: Mechanistic study of hydroamination of alkyne through tantalum-based silicasupported surface species. ACS Catalysis.

Cited by 15 publications

References 24 publications

Evidence for Silica Surface Three- and Five-Membered Metallacycle Intermediates in the Catalytic Cycle of Hydroaminoalkylation of Olefins Using Single-Ti-Metal Catalysts

Evidence for Silica Surface Three- and Five-Membered Metallacycle Intermediates in the Catalytic Cycle of Hydroaminoalkylation of Olefins Using Single-Ti-Metal Catalysts

Surface Organometallic Chemistry on Zeolites: Synthesis of Group IV Metal Alkyls and Metal Hydrides on Hierarchical Mesoporous H-ZSM-5

Enhanced Catalysis Based on the Surface Environment of the Silica-Supported Metal Complex

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