Search results for: Pavel A. Zhizhko

Items from 1 to 13 out of 13 results

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Design of 4‐Coordinate Ti Imido Aryloxide on the Surface of Silica for Catalytic Oxo/Imido Heterometathesis

Andrey V. Pichugov, Nikolai S. Bushkov, Andrey V. Rumyantsev, Anton A. Zhizhin, more

Helvetica Chimica Acta > 105 > 6 > n/a - n/a

We report here the synthesis of 4‐coordinate Ti imido complexes Ti(=N^tBu)(OAr_tBu)₂(py) (2) and Ti(=N^tBu)(OAr_tBu)(Me₂Pyr)(py) (3) (Ar_tBu=O‐2,6‐^tBu₂‐4‐MeC₆H₂, Me₂Pyr=2,5‐dimethylpyrrolyl) and study their grafting onto the surface of partially dehydroxylated silica with the aim to prepare 4‐coordinate Ti imido aryloxide surface species. Study of the resulting materials with IR, solid‐state NMR, elemental...

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Metal‐Surface Interactions and Surface Heterogeneity in ‘Well‐Defined’ Silica‐Supported Alkene Metathesis Catalysts: Evidences and Consequences

Margherita Pucino, Wei‐Chih Liao, Ka Wing Chan, Erwin Lam, more

Helvetica Chimica Acta > 103 > 6 > n/a - n/a

Here we present our observations on a peculiar kinetic behavior observed at low catalyst loadings for the metathesis of internal olefins on a highly active silica‐supported tungsten oxo alkylidene prepared through surface organometallic chemistry (SOMC). The observed kinetic profile is comprised of two consecutive regimes, which support the presence of two different active sites on the surface of...

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Molecular and Silica‐Supported Mo and W d⁰ Imido‐Methoxybenzylidene Complexes: Structure and Metathesis Activity

Pavel A. Zhizhko, Florian Toth, Christopher P. Gordon, Ka Wing Chan, more

Helvetica Chimica Acta > 102 > 10 > n/a - n/a

5‐Coordinated methoxybenzylidene complexes M(=NAr)(=CH−C₆H₄−o‐OMe)(O^tBu_F3)₂ (Ar=2,6‐ⁱPr₂C₆H₃; ^tBu_F3=CMe₂(CF₃)) of Mo (1m_Mo) and W (1m_W) were synthesized by cross‐metathesis from the corresponding neophylidene/neopentylidene precursors and o‐methoxystyrene. 1m_Mo and 1m_W were grafted onto the surface of silica partially dehydroxylated at 700 °C to give well‐defined silica‐supported alkylidenes (≡SiO)M(=NAr)(=CH−C...

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Binuclear and Hexanuclear Ti(IV) Complexes Supported by [OOOO]^4–-type Ligand for Preparing Disentangled UHMWPE

Vladislav A. Tuskaev, Svetlana Ch. Gagieva, Dmitry A. Kurmaev, Viktor G. Vasil’ev, more

Chinese Journal of Polymer Science > 2019 > 37 > 5 > 471-477

Binuclear and hexanuclear titanium complexes stabilized by tetradentate [OOOO]^4–-type ligand were active in ethylene polymerization in the presence of Et₂AlCl/Bu₂Mg binary co-catalyst, giving high molecular weight polyethylene. The binuclear complex showed significantly higher catalytic activity and thermal stability in comparison to mononuclear analogue. Ultra high molecular weight polyethylene (UHMWPE)...

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Catalytic Oxo/Imido Heterometathesis by a Well‐Defined Silica‐Supported Titanium Imido Complex

Pavel A. Zhizhko, Andrey V. Pichugov, Nikolai S. Bushkov, Florian Allouche, more

Angewandte Chemie International Edition > 57 > 34 > 10879 - 10882

Grafting Ti(=NtBu)(Me₂Pyr)₂(py)₂ (Me₂Pyr= 2,5‐dimethylpyrrolyl, py=pyridine) onto the surface of silica partially dehydroxylated at 700 °C gives the well‐defined silica‐supported Ti imido complex (≡SiO)Ti(=NtBu)(Me₂Pyr)(py)₂, which is fully characterized by IR and solid‐state NMR spectroscopy as well as elemental and mass balance analyses. While stoichiometric imido‐transfer reactivity is typical...

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Catalytic Oxo/Imido Heterometathesis by a Well‐Defined Silica‐Supported Titanium Imido Complex

Pavel A. Zhizhko, Andrey V. Pichugov, Nikolai S. Bushkov, Florian Allouche, more

Angewandte Chemie > 130 > 34 > 11045 - 11048

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Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

Christophe Copéret, Florian Allouche, Ka Wing Chan, Matthew P. Conley, more

Angewandte Chemie International Edition > 57 > 22 > 6398 - 6440

Many industrial catalysts contain isolated metal sites on the surface of oxide supports. Although such catalysts have been used in a broad range of processes for more than 40 years, there is often a very limited understanding about the structure of the catalytically active sites. This Review discusses how surface organometallic chemistry (SOMC) engineers surface sites with well‐defined structures...

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Eine Brücke zwischen industriellen und wohldefinierten Trägerkatalysatoren

Christophe Copéret, Florian Allouche, Ka Wing Chan, Matthew P. Conley, more

Angewandte Chemie > 130 > 22 > 6506 - 6551

Viele industrielle Katalysatoren enthalten isolierte Metallzentren an der Oberfläche von Oxidträgern. Derartige Katalysatoren werden seit über 40 Jahren bei verschiedensten Verfahren verwendet – die Struktur ihrer katalytischen Zentren bleibt aber bis heute nur ungenügend verstanden. Dieser Aufsatz zeigt, wie mit metallorganischer Oberflächenchemie (SOMC) Oberflächenzentren mit gut definierten Strukturen...

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Benchmarked Intrinsic Olefin Metathesis Activity: Mo vs. W

Pavel A. Zhizhko, Victor Mougel, Jordan De Jesus Silva, Christophe Copéret

Helvetica Chimica Acta > 101 > 3 > n/a - n/a

Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well‐defined silica‐supported Mo and W imido‐alkylidenes show very similar activities in metathesis of internal olefins, Mo catalysts systematically outperform their...

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Surface Organometallic Chemistry: Paving the Way Beyond Well-Defined Supported Organometallics and Single-Site Catalysis

Christophe Copéret, Alexey Fedorov, Pavel A. Zhizhko

Catalysis Letters > 2017 > 147 > 9 > 2247-2259

The molecular approach to single-site and nanoparticle-based heterogeneous catalysts relies on a stringent control over the surface chemistry, enabled by the judicious choice of dehydroxylated supports and tailored organometallic precursors. Aided by the advanced characterization methods, the field of surface organometallic chemistry (SOMC) has provided molecular-level insights into the mechanism...

article

Oxo/imido heterometathesis between N-sulfinylamines and ketones catalyzed by a silica-supported molybdenum imido complex

Pavel A. Zhizhko, Anton A. Zhizhin, Dmitry N. Zarubin, Nikolai A. Ustynyuk

Mendeleev Communications > 2012 > 22 > 2 > 64-66

Grafting the molecular complex (MesN)2Mo(CH2CMe2Ph)2 onto the surface of silica dramatically enhances its catalytic activity in the oxo/imido heterometathesis reaction of N-sulfinylamines with carbonyl compounds.

article

Oxo/imido heterometathesis of N-sulfinylamines and carbonyl compounds catalyzed by silica-supported vanadium oxochloride

Pavel A. Zhizhko, Anton A. Zhizhin, Dmitry N. Zarubin, Nikolai A. Ustynyuk, more

Journal of Catalysis > 2011 > 283 > 1 > 108-118

A series of silica-supported vanadium oxo complexes has been prepared via water-free grafting VOCl ₃ onto the silica surface. The obtained materials have been characterized with Raman, diffuse reflectance FTIR (DRIFT) and UV–vis, ⁵¹ V solid-state NMR and X-ray photoelectron spectroscopies, elemental analysis and N ₂ physisorption. The samples with a low vanadium loading (1–5%)...

article

Niobium/Rhodium Bimetallic Complexes: Synthesis, Structure, and Catalytic Hydrosilylation of Acetophenone and Benzaldehyde

Somying Leelasubcharoen, Pavel A. Zhizhko, Lyudmila G. Kuzmina, Andrei V. Churakov, more

Organometallics > 2009 > 28 > 15 > 4500 - 4506

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