ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTScandium complex [{(.eta.5-C5Me4)Me2Si(.eta.1-NCMe3)}(PMe3)ScH]2: a unique example of single-component .alpha.-olefin polymerization catalystPamela J. Shapiro, Emilio Bunel, William P. Schaefer, and John E. BercawCite this: Organometallics 1990, 9, 3, 867–869Publication Date (Print):March 1, 1990Publication History Published online1 May 2002Published inissue 1 March...

The evolution of organoscandium chemisty in our research group over the past ten years is described. synthesis well-defined, mononuclear compounds challenging due to propensity highly Lewis acidic scandium center induce oligomerization with formation {Sc-(μ-R)-Sc} bridges. By using two bulky pentamethylcyclopentadienyl (Cp*) ligands, thermally stable, monomeric hydride and hydrocarbyl derivatives type Cp*2Sc-R (R = H, alkyl, aryl, alkyl) have been obtained. Due primarily their extreme...

[reaction: see text] New air-stable PdCl(2){P(t)Bu(2)(p-R-Ph)}(2) (R = H, NMe(2), CF(3),) complexes represent simple, general, and efficient catalysts for the Suzuki-Miyaura cross-coupling reactions of aryl halides including five-membered heteroaryl heteroatom-substituted six-membered chlorides with a diverse range arylboronic acids. High product yields (89-99% isolated yields) turn-over-numbers (10,000 TON) are observed.

We systematically investigated the role of surface modification nanoparticles catalyst in alkyne hydrogenation reactions and proposed general explanation effect ligands on selectivity activity Pt Co/Pt (NPs) using experimental computational approaches. show that proper balance between adsorption energetics alkenes at NPs as compared to capping defines nanocatalyst for alkene reaction. report addition primary alkylamines CoPt3 can drastically increase from 0 more than 90% with ∼99.9%...

X-ray absorption spectroscopy and in situ electron paramagnetic resonance evidence were provided for the reduction of Cu(II) to Cu(I) species by alkynes presence tetramethylethylenediamine (TMEDA), which TMEDA plays dual roles as both ligand base. The structures starting obtained determined (TMEDA)CuCl2 [(TMEDA)CuCl]2 dimer, respectively.

An efficient alkyne C-H activation and homocoupling procedure has been studied which indicates that a Cu(II)/Cu(I) synergistic cooperation might be involved. In situ Raman spectroscopy was employed to study kinetic behavior, drawing the conclusion Cu(I) rather than Cu(II) participates in rate-determining step. IR, EPR, X-ray absorption evidence were provided for structural information, indicating stronger interaction with Kinetics showed plays role as oxidant C-C bond construction step, fast...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural and Physical Properties of Delocalized Mixed-Valent [Cp*M(pentalene)M'Cp*]n+ [Cp*M(indacene)M'Cp*]n+ (M, M' = Fe, Co, Ni; n 0, 1, 2) ComplexesJuan M. Manriquez, Michael D. Ward, William Reiff, Joseph C. Calabrese, Nancy L. Jones, Patrick J. Carroll, Emilio E. Bunel, Joel S. MillerCite this: Am. Chem. Soc. 1995, 117, 23, 6182–6193Publication Date (Print):June 1995Publication History Published online1 May 2002Published inissue 1 June...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbon-carbon bond activation via .beta.-alkyl elimination. Reversible branching of 1,4-pentadienes catalyzed by scandocene hydride derivativesEmilio. Bunel, Barbara J. Burger, and John E. BercawCite this: Am. Chem. Soc. 1988, 110, 3, 976–978Publication Date (Print):February 1988Publication History Published online1 May 2002Published inissue 3 February...

The new air-stable PdCl2{PR2(Ph-R')}2 complexes, readily prepared from commercial reagents, exhibit unique efficiency as catalysts for the Suzuki−Miyaura coupling reactions of a variety heteroatom-substituted heteroaryl chlorides with diverse range aryl/heteroaryl boronic acids. catalyzed by complexes high product yields (88−99%) and catalyst turnover numbers (up to 10 000 TON).

Carbenes with a twist: A seven-membered N-heterocyclic carbene (NHC) ligand is prepared from an amidinium precursor, derived 2,2′-dinitrobiphenyl, and yields the NHC–PdII complex [PdCl(allyl)(NHC)] (see scheme). This framework exhibits tortional twist that results in axial symmetry. class can be readily modified attractive for future application asymmetric catalysis. Supporting information this article available on WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z501522_s.pdf or...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPentamethylcyclopentadienyl acetylacetonate complexes of iron(II), cobalt(II), and nickel(II). Convenient synthetic entries to mono-.eta.5-C5Me5 derivativesEmilio E. Bunel, Luis. Valle, Juan M. ManriquezCite this: Organometallics 1985, 4, 9, 1680–1682Publication Date (Print):September 1, 1985Publication History Published online1 May 2002Published inissue 1 September 1985https://doi.org/10.1021/om00128a034RIGHTS & PERMISSIONSArticle...

A mild, general, catalytic system for the alpha-vinylation of carbonyl compounds has been developed. By employing [Pd(P(t)Bu(3))Br](2) as catalyst and LHMDS base, vinyl bromides, triflates, tosylates couple with 3-methyloxindole in satisfactory yields. The same is extended to ketones esters.

A novel oxidative C-H/C-H cross-coupling reaction between electron-rich arenes and alkenes is established utilizing FeCl3 as the catalyst DDQ oxidant. Interestingly, direct arylation products are obtained with diaryl-ethylenes double styrene derivatives, which show high chemoselectivity good substrate scope. radical trapping experiment EPR (electron paramagnetic resonance) experiments indicate that this proceeds through a pathway in plays key role aryl formation. XAFS (X-ray absorption fine...

Five different first-row transition metal precursors (V(III), Cr(III), Mn(II), Co(II), Ni(II)) were successfully incorporated into a catechol porous organic polymer (POP) and characterized using ATR-IR XAS analysis. The resulting metallated POPs then evaluated for catalytic alkyne hydrogenation high-throughput screening techniques. All unexpectedly found to be active selective catalysts semihydrogenation. Three of the (V, Cr, Mn) are first their kind single-site catalysts. These results...

A stable and structurally well-defined titanium alkoxide catalyst supported on a metal–organic-framework (MOF) of UiO-67 topology (ANL1-Ti(OiPr)2) was synthesized fully characterized by variety analytical spectroscopic techniques, including BET, TGA, PXRD, XAS, DRIFT, SEM, DFT computations. The Ti-functionalized MOF demonstrated active for the catalytic hydroboration wide range aldehydes ketones with HBpin as boron source. Compared to traditional homogeneous catalysts, ANL1-Ti(OiPr)2 is...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBis[(pentamethylcyclopentadienyl)metal]pentalenes. A new class of highly delocalized, fused metallocenesEmilio E. Bunel, Luis. Valle, Nancy L. Jones, Patrick J. Carroll, Cecilia. Barra, Myriam. Gonzalez, Nancy. Munoz, Giovanni. Visconti, Arie. Aizman, and Juan M. ManriquezCite this: Am. Chem. Soc. 1988, 110, 19, 6596–6598Publication Date (Print):September 1, 1988Publication History Published online1 May 2002Published inissue 1 September...

A variety of 4-oxobutenamides 1 were subjected to rhodium-catalyzed conjugate addition with arylboronic acids providing high regio- and enantioselectivity (97:3 >99:1, >96% ee) moderate excellent yields (54-99%). The key selectivity is the use sterically demanding P-chiral diphosphines, such as Tangphos or Duanphos. product oxobutanamides 2 may be converted alternate targets by selective derivatization either amide ketone functional group. stereochemical model predicting absolute sense...

A mechanistic study on the zinc-promoted coupling between aldehydes and terminal alkynes was demonstrated. bimetallic zinc complex determined to be active species.

Abstract The Cu I /Cu II and III catalytic cycles have been subject to intense debate in the field of copper‐catalyzed oxidative coupling reactions. A mechanistic study on redox process, by X‐ray absorption (XAS) electron paramagnetic resonance (EPR) spectroscopies, has elucidated reduction mechanism 1,3‐diketone detailed investigation revealed that halide ion is important for process. nature thereby‐formed also studied XAS EPR spectroscopy. This information applicable cyclization...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSyntheses of p-phenylene- and p-biphenylylene-bridged methylated binuclear ferrocenesEmilio E. Bunel, Pedro. Campos, Jose. Ruz, Luis. Valle, Isabel. Chadwick, Maria. Santa Ana, Guillermo. Gonzalez, Juan M. ManriquezCite this: Organometallics 1988, 7, 2, 474–476Publication Date (Print):February 1, 1988Publication History Published online1 May 2002Published inissue 1 February...

Application of CO2 as a renewable feedstock and C1 building block for production commodity fine chemicals is highly challenging but obvious industry-relevant task. Of particular interest the catalytic coupling with inexpensive unsaturated hydrocarbons (olefins, dienes, styrenes, alkynes), providing direct access to carboxylic acids their derivatives. Although not brand new scientific community, it still complete challenge, no truly effective system has been reported date. In this...

The adsorption of transition metal oleates on Pt nanoparticle surfaces creates a negative charge, promoting selective hydrogenation CO bonds over CC in nonpolar solvents, ensuring reactant solubility and improving catalytic efficiency.