Both industrial and biochemical ammonia syntheses are thought to rely on the cooperation of multiple metals in breaking strong triple bond dinitrogen. Such multimetallic for dinitrogen cleavage is also general rule reductive with molecular systems surfaces. We have observed at 250 degrees C atmospheric pressure by dihydrogen isolated silica surface-supported tantalum(III) tantalum(V) hydride centers [(identical Si-O)2Ta(III)-H] Si-O)2Ta(V)H3], leading Ta(V) amido imido product...

The reaction of [W(NAr)(CHtBu)(CH2tBu)2] (1; Ar = 2,6-iPrC6H3) with a silica partially dehydroxylated at 700 °C, SiO2-(700), gives syn-[(⋮SiO)W(NAr)(CHtBu)(CH2tBu)] (2) as major surface species, which was fully characterized by mass balance analysis, IR, NMR, EXAFS, and DFT periodic calculations. Similarly, complex 1 reacts [(c-C5H9)7Si7O12SiOH] to give [(SiO)W(NAr)(CHtBu)(CH2tBu)] (2m), shows similar spectroscopic properties. Surface 2 is highly active propene metathesis catalyst, can...

The reaction of [Ta(CHtBu)(CH2tBu)3] or [Cp*Ta(CH3)4] with a silica partially dehydroxylated at 700 °C gives the corresponding monosiloxy surface complexes [(⋮SiO)Ta(CHtBu)(CH2tBu)2] and [(⋮SiO)Ta(CH3)3Cp*] by eliminating σ-bonded ligand as alkane (H−CH2tBu H−CH3). EXAFS data show that an adjacent siloxane bridge plays role extra ligand, which most likely stabilizes these in [(⋮SiO)Ta(CHtBu)(CH2tBu)2(⋮SiOSi⋮)] (1a') [(⋮SiO)Ta(CH3)3Cp*(⋮SiOSi⋮)] (2a'). In case...

The reaction of [([triple bond]SiO)Zr(CH(2)tBu)(3)] with H(2) at 150 degrees C leads to the hydrogenolysis zirconium-carbon bonds form a very reactive hydride intermediate(s), which further reacts surrounding siloxane ligands present surface this support mainly two different zirconium hydrides: bond]SiO)(3)Zr-H] (1a, 70-80%) and bond]SiO)(2)ZrH(2)] (1b, 20-30%) along silicon hydrides, bond]SiO)(3)SiH] bond]SiO)(2)SiH(2)]. Their structural identities were identified by (1)H DQ solid-state NMR...

Flame silica was surface-labeled with (17)O, through isotopic enrichment of both siloxanes and silanols. After heat treatment at 200 700 °C under vacuum, the resulting partially dehydroxylated materials were investigated by high-field solid-state (1)H (17)O NMR. More specifically, MQ MAS HMQC sequences used to probe local environment. In a further step, these (17)O-tagged supports for preparation supported catalysts reaction perhydrocarbyl transition metal derivatives (zirconium tetraalkyl,...

The molecular complex [Re(=CtBu)(=CHtBu)(CH2tBu)2] 1 reacts with a silica partially dehydroxylated at 700 degrees C to give syn-2, [(=SiO)Re(=CtBu)(=CHtBu)(CH2tBu)], as single isomer according mass-balance analysis, IR, and solid-state NMR spectroscopy. 1D 2D (HETCOR long-range HETCOR) on 13C-labeled-2 has allowed us observe the chemical shifts of all carbons (including those that are not labeled) ascertain their assignments. Moreover, EXAFS data consistent presence two relatively short...

The Ta(CHtBu)(CH2tBu)3 complex 1 reacts with the OH groups of a MCM-41 mesoporous silica dehydroxylated at 500 °C to form monosiloxy surface species [(⋮SiO)Ta(CHtBu)(CH2tBu)2] 2, evolution equiv per Ta neopentane. Complex 2 leads mixture supported tantalum hydrides [(⋮SiO)2Ta(H)x] (x = 1, 3), 3, by treatment under hydrogen 150 °C. These complexes were characterized combined use several techniques such as IR and EXAFS spectroscopies well 1H MAS, 13C CP/MAS, 2D 1H−13C HETCOR, J-resolved...

We report the first radical reaction of tetrazenes – i. e. functions with four consecutive nitrogen atoms a linear N–N=N–N chain that retains characteristic 4N pattern. Selective hydrogen atom transfer (HAT) in α‐position enables free polymerization various polar and non‐polar monomers. The tetrazene units play dual role. Its decomposition generates aminyl radicals can undergo HAT lead to initiating C‐centered radicals. Contrary what was previously thought never add polymers obtained feature...

We report the first radical reaction of tetrazenes – i. e. functions with four consecutive nitrogen atoms a linear N–N=N–N chain that retains characteristic 4N pattern. Selective hydrogen atom transfer (HAT) in α‐position enables free polymerization various polar and non‐polar monomers. The tetrazene units play dual role. Its decomposition generates aminyl radicals can undergo HAT lead to initiating C‐centered radicals. Contrary what was previously thought never add polymers obtained feature...

The molecular complex [W(⋮CtBu)(CH2tBu)3], 1, reacts with SiO2-(700) to give as major species 2a, [(⋮SiO)W(⋮CtBu)(CH2tBu)2], while a bisgrafted surface 3a, [(⋮SiO)2W(⋮CtBu)(CH2tBu)], is obtained on SiO2-(200). As in organometallic chemistry, the alkylalkylidyne tautomeric form favored. Despite these structural features, complexes are very active olefin metathesis catalysts, reported earlier, and it likely that necessary metallocarbene intermediates generated under reaction conditions.

The MCM-41 supported hydrides [([triple bond]SiO)(2)TaH(3)], 1a, and 1b, cleave N-H bonds of ammonia at room temperature to yield the well-defined imido amido surface complexes bond]SiO)(2)Ta(NH)(NH(2))], 2, 2xNH(3). Additionally, silanes [[triple bond]Si-H] that exist in close proximity 1a 1b also react with give silylamido [Si-NH(2)]. Such reaction is tantalum assisted: were synthesized independently absence by highly strained silica, SiO(2-1000), SiH(4) no was observed. Surface-supported...

A minor species, generated by CH activation of the methyl group CH3ReO3 on reactive surface sites alumina, is active site alumina-supported CH3ReO3, a highly olefin metathesis catalyst, while major formed coordination at same sites, inactive (see scheme; Os denotes O atoms alumina surface).

Anhydrous Keggin-type phosphorus heteropolyacids were deposited on partially dehydroxylated silica by using the surface organometallic chemistry (SOMC) strategy. The resulting solids characterized a combination of physicochemical methods including IR, Raman, 1D and 2D 1H, 31P MAS NMR, electron microscopy experiments density functional theory (DFT) calculations. It is shown that main species [≡Si(OH...H+)]2[H+]1[PM12O403−] where polyoxometalate linked to support proton interaction with two...

Impregnation of [(AliBu(3))(Et(2)O)] on partially dehydroxylated SBA-15 affords a mesoporous material bearing the well-defined single site surface aluminium species [(≡SiO)(2)Al(iBu)(Et(2)O)].

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTCharacterization of Surface Organometallic Complexes Using High Resolution 2D Solid-State NMR Spectroscopy. Application to the Full Characterization a Silica Supported Metal Carbyne: ⋮SiO−Mo(⋮C−Bu-t)(CH2−Bu-t)2Romain Petroff Saint-Arroman, Mathieu Chabanas, Anne Baudouin, Christophe Copéret, Jean-Marie Basset, Lesage, and Lyndon EmsleyView Author Information Laboratoire de Chimie OrganoMétallique UMR 9986 CNRS-ESCPE Lyon 43 bd du 11 Novembre...

Trialkylimidazolium chlorozincate molten salts resulting from the combination of zinc chloride and 1-butyl-2,3-dimethylimidazolium chloride, [BMMI][Cl], have been prepared with a mole percent ZnCl2, R (R = nZnCl2/nZnCl2 + n[BMMI][Cl]) equal to 0, 0.1, 0.25, 0.33, 0.5, 0.66, 0.75. Their analyses by DSC, 13C, 1H 35Cl solid state solution NMR, mass spectrometry (ESI, MS/MS) are consistent presence [BMMI][Cl] [BMMI][ZnCl3] for < 0.5; pure [BMMI][Zn3Cl7] > 0.5. Infrared spectra realized in...

Abstract Grafting of [W(C‐ t‐ Bu)(CH 2 ‐ Bu) 3 ] ( 1 ) on silica‐alumina partially dehydroxylated at 500 °C generates a surface complex [(SiO)W(C‐ as evidenced by mass balance analysis, IR, and NMR spectroscopy. Upon treatment this species under H , tungsten hydride derivative, [(SiO)(EO)W(H) x ), (E=Si or Al), is formed. Both these complexes are active alkane metathesis catalysts. The activity similar to that observed for the hydride‐supported alumina much greater than obtained silica....

Surface details: Aluminum hydrides supported on partially dehydroxylated alumina have been synthesized through the hydrogenolysis of grafted alkyl precursors. The key feature in multinuclear NMR studies with these species is strong dipolar coupling between 1H and 27Al nuclei. In HMQC correlations, Al–H entities were identified by filtering out signal Al2O3 bulk (see picture). These main-group-metal catalyze both ethylene polymerization hydrogenation. Detailed facts importance to specialist...

Supported metathesis: Grafting (CH3)ReO3 onto alumina covered with surface trimethylsilyl groups increases the efficiency and selectivity of this catalyst in olefin metathesis (see scheme). The SiMe3 (X) modify adsorption properties by favoring desorption thereby disfavoring secondary reactions. Supporting information for article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z704876_s.pdf or from author. Please note: publisher not responsible content functionality...

Non-oxidative coupling of methane with high selectivity into ethane (>99% among hydrocarbon) in a classical fixed-bed reactor catalysed by SiO(2)-Al(2)O(3) or gamma-Al(2)O(3) supported tungsten hydride is presented. Continuous hydrogen separation, using Pd-Ag membrane reactor, led to far beyond the thermodynamic equilibrium conversion.