The combination of VCl3(THF)3 and N,N-bis(trimethylsilyl)aniline (1a) is an efficient catalyst for the [2+2+1] coupling reaction alkynes azobenzenes, giving multisubstituted pyrroles. A plausible mechanism involves generation a mono(imido)vanadium(III) species as initiation step, where 1a served imido source with concomitant release 2 equiv ClSiMe3, followed by azobenzene to form catalytically active bis(imido)vanadium(V) via N═N bond cleavage.

Titania-supported vanadia (VO x /TiO2) catalysts exhibit outstanding catalytic in a number of selective oxidation and reduction processes. In spite numerous investigations, the nature redox transformations vanadium titanium involved various processes remains difficult to detect correlate rate products formation. this work, we studied dynamics active sites bilayered 5% V2O5/15% TiO2/SiO2 catalyst (consisting submonolayer VO species anchored onto TiO monolayer, which turn is supported on SiO2)...

N-heterocyclic carbenes (NHCs) have emerged as versatile ligands in organometallic chemistry, prized for their strong σ-donating and tunable electronic properties. They stabilize diverse motifs, well clusters, nanoparticles, particularly those based on the coin-age metals—Cu, Ag, Au. Importantly, carbene 13C NMR isotropic chemical shift (δiso) of NHC-coinage metal complexes varies significantly across these elements, reflecting nuanced interplay structural factors. Here, we investigate...

Ti-catalyzed alkyne diamination and hydrohydrazination proceed through a common N-aminoazatitanacyclobutene intermediate. These reactions have historically existed as processes catalyzed by distinct molecular Ti compounds, with several reports for only single example diamination. Here, we demonstrate that diamidoamine catalyst, (NNN)Ti(═NNR2) (1, (NNN)H2 = N-methyl-N',N″-bis(trimethylsilyl)diethylenetriamine; R alkyl, aryl), is capable of catalyzing both hydrohydrazination, where the...

InfoMetricsFiguresRef. The Journal of Physical Chemistry CASAPArticle This publication is free to access through this site. Learn More CiteCitationCitation and abstractCitation referencesMore citation options ShareShare onFacebookXWeChatLinkedInRedditEmailBlueskyJump toExpandCollapse ORIGINAL ARTICLE. notice a correction.Addition/CorrectionMarch 26, 2025Correction "Fingerprint Analysis X-ray Absorption Spectra with the Machine-Learning Method Trained on Multielement Experimental...

Low-valent tungsten species generated from WCl6 and N,N′-bis(trimethylsilyl)-2,5-dimethyldihydropyrazine (Si-Me2-DHP) promotes the catalytic formation of N-phenyl-2,3,4,5-tetraarylpyrroles 3aa-ka diarylacetylenes 1a-k azobenzene (2a). An initial catalyst activation process is a three-electron reduction with Si-Me2-DHP to afford transient 'WCl3' species. Catalytically active bis(imido)tungsten(VI) via successive one-electron N═N bond cleavage 2a was revealed by isolating W(═NPh)2Cl2(PMe2Ph)2...

Terminal imido complexes containing metal–nitrogen multiple bonds have been widely used in organometallic chemistry and homogeneous catalysis. The role of terminal ligands spans from reactive sites to spectator motifs, largely depending on the nature metal center its specific coordination sphere. Aiming at identifying reactivity descriptors for M–N bonds, we herein explore solid-state 15N NMR spectroscopy (ssNMR) early transition augmented by computational studies show that asymmetry...

X-ray absorption spectroscopy (XAS) has been central to the study of Phillips polymerization catalyst (CrO 3 /SiO 2 ).

Terminal imido complexes, containing metal-nitrogen multiple bonds, have been widely used in organometallic chemistry and homogeneous catalysis. The role of terminal ligands span from reactive site to spectator motif, largely depending on the nature metal center its specific coordination sphere. Aiming at identifying reactivity descriptors for M-N we herein explore solid-state 15N NMR spectroscopy (ssNMR) early-transition complexes augmented by computational studies show that asymmetry...

We report the syntheses of 2-pyridylimido complexes tantalum and niobium by N═N bond cleavage 2,2′-azopyridine. Reaction MCl5 (M = Ta Nb) with 2,2′-azopyridine in presence 0.5 equiv 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene (abbreviated Si-Me-CHD) afforded a dark red solution (for Ta) blue some insoluble precipitates. After removing solids, another Si-Me-CHD was added to each solution, giving [M(═Npy)Cl3]n (1a: M Ta; 1b: through reductive The initial products above reactions were...

Treatment of Ziegler-Natta (ZN) catalysts with BCl3 improves their activity by increasing the number active sites. Here we show how 47/49Ti solid-state nuclear magnetic resonance (NMR) spectroscopy enables to understand electronic structure Ti surface sites present in such ZN pre-catalysts, prior activation alkyl aluminium. High-field (21.1 T) and low temperature (~100 K) NMR augmented DFT modelling on pre-catalyst corresponding molecular analogues detection signatures a level understanding...

Treatment of Ziegler-Natta (ZN) catalysts with BCl3 improves their activity by increasing the number active sites. Here we show how 47/49Ti solid-state nuclear magnetic resonance (NMR) spectroscopy enables to understand electronic structure Ti surface sites present in such ZN pre-catalysts, prior activation alkyl aluminium. High-field (21.1 T) and low temperature (~100 K) NMR augmented DFT modelling on pre-catalyst corresponding molecular analogues detection signatures a level understanding...

Treatment of Ziegler-Natta (ZN) catalysts with BCl3 improves their activity by increasing the number active sites. Here we show how 47/49Ti solid-state nuclear magnetic resonance (NMR) spectroscopy enables us to understand electronic structure Ti surface sites present in such treated ZN pre-catalysts, prior activation alkyl aluminum. High-field (21.1 T) and low-temperature (∼100 K) NMR augmented DFT modeling on pre-catalyst corresponding molecular analogues detection signatures a level...

Olefin metathesis has been established as an efficient tool to build carbon-carbon bonds, and its widespread applications in organic synthesis have made possible by the development of homogeneous catalysts – Grubbs Schrock-type that operate through same intermediates Chauvin mechanism. With d0 catalysts, first elementary step, olefin-coordination, is often rate determining, but it rarely explored due lack accessible relevant molecular analogs. Here, we develop a surrogate this key...

Since its emergence over 50 years ago, the structure of surface sites in Ziegler–Natta catalysts, which are responsible for a major fraction world's supply polyethylene (PE) and polypropylene (PP), has remained elusive. This is part due to complexity these systems that involve multiple synthetic steps components, namely, MgCl2 support, transition-metal chloride, several organic modifiers, known as donors, used prior some instances during activation step with alkyl aluminum. Due favorable...

Since its emergence over 50 years ago, the structure of surface sites in Ziegler-Natta catalysts, which are responsible for a major fraction world’s supply polyethylene (PE) and polypropylene (PP), has remained elusive. This is part due to complexity systems that involve multiple synthetic steps components, namely MgCl2 support, transition-metal chloride (commonly TiCl4), several organic modifiers, known as donors, used prior some instances during activation step with alkyl aluminum. Due...

Low-valent tungsten species generated from WCl6 and N,N’-bis(trimethylsilyl)-2,5-dimethyldihydropyrazine (Si-Me2-DHP) promotes catalytic formation of N-phenyl-2,3,4,5-tetraarylpyrroles 3aa-ka diarylacetylenes 1a-k azobenzene (2a). An initial catalyst activation process is a three-electron reduction with Si-Me2-DHP to afford transient ‘WCl3‘ species. Catalytically active bis(imido)tungsten(VI) via successive one-electron N=N bond cleavage 2a was revealed by isolating W(=NPh)2Cl2(PMe2Ph)2...

The Union Carbide (UC) ethylene polymerization catalysts, based on chromocene dispersed silica, show distinct features from the Phillips but share same heated debate regarding structure of their active sites. Based a combination IR, EPR spectroscopies, labeling experiments, and DFT modeling, we identified monomeric surface-supported Cr(iii) hydrides, ([triple bond, length as m-dash]SiO)Cr(Cp)-H, sites UC catalyst. These are formed in presence grafted adsorbed well residual surface OH groups,...

Ziegler-Natta (ZN) catalysts – typically formulated as TiCl4/MgCl2/AlR3 and possibly containing additional organic ligands are essential to the production of polyethylene polypropylene. Despite their industrial relevance years research on these materials, role each constituent (support, ligands, post-treatment with or inorganic modifiers…) structure Ti surface sites responsible for polymerization remains poorly understood, partly because high complexity such materials. Herein, we show how...

X-ray absorption spectroscopy (XAS) is one of the most powerful characterization techniques, that has been intensively employed to study Phillips polymerization catalyst (CrO3/SiO2). While Cr K-edge XAS signatures are used evaluate nature surface (active) sites, they highly sensitive oxidation state, geometry and types ligands, making interpretation challenging. In specific case CrO3/SiO2, CO particularly both as a reductant generate expected low valent sites probe understand sites....

Ziegler-Natta (ZN) catalysts – typically formulated as TiCl4/MgCl2/AlR3 and possibly containing additional organic ligands are essential to the production of polyethylene polypropylene. Despite their industrial relevance years research on these materials, role each constituent (support, ligands, post-treatment with or inorganic modifiers etc.) structure Ti surface sites responsible for polymerization remains poorly understood, partly because high complexity such materials. Herein, we show...

Since its emergence over 50 years ago, the structure of surface sites in Ziegler-Natta catalysts, which are responsible for a major fraction world’s supply polyethylene (PE) and polypropylene (PP), has remained elusive. This is part due to complexity systems that involve multiple synthetic steps components, namely MgCl2 support, transition-metal chloride, several organic modifiers, known as donors, used prior some instances during activation step with alkyl aluminum. Due favorable NMR...

Terminal imido complexes, containing metal-nitrogen multiple bonds, have been widely used in organometallic chemistry and homogeneous catalysis. The role of terminal ligands span from reactive site to spectator motif, largely depending on the nature metal center its specific coordination sphere. Aiming at identifying reactivity descriptors for M-N we herein explore solid-state 15N NMR spectroscopy (ssNMR) early-transition complexes augmented by computational studies show that asymmetry...