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Léon Witteman, Martin Lutz, Marc-Etienne Moret
N-Heterocycle-substituted silyl iron complexes have been synthesized by nucleophilic substitution at trichlorosilyl ligands bound to iron. The homoleptic (tripyrrolyl)- and tris(3-methylindolyl)silyl groups were accessed from (Cl3 Si)CpFe(CO)2 (Cl3 SiFp) by substitution of chloride with pyrrolide or 3-methylindolide, respectively. Analogously, nucleophilic substitution of Cl with pyrrolide on the anionic Fe(0) synthon Cl3 SiFe(CO)4 - generates the (tripyrrolyl)silyl ligand, bound to the iron tetracarbonyl fragment...
September 24, 2018: Organometallics
Jessica M Weber, Ashley R Longstreet, Timothy F Jamison
Herein, we report the synthesis and characterization of a new class of air- and moisture-stable phosphine-containing nickel(II) precatalysts, which activate through a Heck-type mechanism. The activities of the precatalysts are demonstrated with a carbonyl-ene coupling reaction.
August 27, 2018: Organometallics
Feng Chen, Isolda Romero-Canelón, Joan J Soldevila-Barreda, Ji-Inn Song, James P C Coverdale, Guy J Clarkson, Jana Kasparkova, Abraha Habtemariam, Martin Wills, Viktor Brabec, Peter J Sadler
We report the synthesis and characterization of four neutral organometallic tethered complexes, [Ru(η6 -Ph(CH2 )3 -ethylenediamine- N -R)Cl], where R = methanesulfonyl (Ms, 1 ), toluenesulfonyl (Ts, 2 ), 4-trifluoromethylbenzenesulfonyl (Tf, 3 ), and 4-nitrobenzenesulfonyl (Nb, 4 ), including their X-ray crystal structures. These complexes exhibit moderate antiproliferative activity toward human ovarian, lung, hepatocellular, and breast cancer cell lines. Complex 2 in particular exhibits a low cross-resistance with cisplatin...
May 29, 2018: Organometallics
Anna Gatti, Abraha Habtemariam, Isolda Romero-Canelón, Ji-Inn Song, Bindy Heer, Guy J Clarkson, Dominga Rogolino, Peter J Sadler, Mauro Carcelli
We report the synthesis, characterization, and antiproliferative activity of organo-osmium(II) and organo-ruthenium(II) half-sandwich complexes [(η6 - p -cym)Os(L)Cl]Cl ( 1 and 2 ) and [(η6 - p -cym)Ru(L)Cl]Cl ( 3 and 4 ), where L = N -(2-hydroxy)-3-methoxybenzylidenethiosemicarbazide ( L1 ) or N -(2,3-dihydroxybenzylidene)-3-phenylthiosemicarbazide ( L2 ), respectively. X-ray crystallography showed that all four complexes possess half-sandwich pseudo-octahedral "three-legged piano-stool" structures, with a neutral N,S-chelating thiosemicarbazone ligand and a terminal chloride occupying three coordination positions...
March 26, 2018: Organometallics
Sofia Ferrer, Antonio M Echavarren
Gold(I) acetylide and σ,π-digold(I) alkyne complexes derived from one prototypical 1,6-enyne and from 7-ethynyl-1,3,5-cycloheptatriene have been prepared and structurally characterized. Their possible role in gold(I)-catalyzed cycloisomerizations has been studied by experiment and by DFT calculations. Gold(I) acetylides are totally unproductive complexes in the absence of Brønsted acids. Similarly, no cyclizations were observed by heating σ,π-digold(I) alkyne digold(I) at least up to 130 °C. Theoretical studies provide a rationale for the much lower reactivity of digold species in reactions of enynes...
March 12, 2018: Organometallics
Siyuan Luo, Maxime A Siegler, Elisabeth Bouwman
Four dimeric nickel(II) complexes [Ni2 Cl2 (BnC2 S)2 ] [ 1 ], [Ni2 Cl2 (BnC3 S)2 ] [ 2 ], [Ni2 (PyC2 S)2 ]Br2 [ 3 ]Br2 , and [Ni2 (PyC3 S)2 ]Br2 [ 4 ]Br2 of four different thiolate-functionalized N-heterocyclic carbene (NHC) ligands were synthesized, and their structures have been determined by single-crystal X-ray crystallography. The four ligands differ by the alkyl chain length between the thiolate group and the benzimidazole nitrogen (two -C2 - or three -C3 - carbon atoms) and the second functionality at the NHC being a benzyl (Bn) or a pyridylmethyl (Py) group...
March 12, 2018: Organometallics
James E Radcliffe, Jay J Dunsford, Jessica Cid, Valerio Fasano, Michael J Ingleson
The relative (to BEt3 ) hydride ion affinity (HIA) of a series of acridine borenium salts has been calculated, with some HIAs found to be similar to that for [Ph3 C]+ . The HIA at the acridine C9 position is controlled by both acridine and the boron substituents, the latter presumably affecting the strength of the B=N bond in the acridane-BY2 products from hydride transfer. Through a range of hydride abstraction benchmarking reactions against organic hydride donors the experimental HIA of [F5 acr-BCat]+ (cat = catechol, F5 acr = 1,2,3,4,7-pentafluoroacridine) has been confirmed to be extremely high and closely comparable to that of [Ph3 C]+ ...
December 26, 2017: Organometallics
Russell J Needham, Abraha Habtemariam, Nicolas P E Barry, Guy Clarkson, Peter J Sadler
We report the synthesis of halido Os(II) p -cymene complexes bearing bidentate chelating phenylazobenzothiazole (AZBTZ) ligands. Unlike the analogous phenylazopyridine (AZPY) complexes, AZBTZ-NMe2 is capable of both N,N -coordination to Os(II) and cyclometalation to form N,C -coordinated species. N,C -Coordination occurs via an azo nitrogen and an ortho carbon on the aniline ring, as identified by 1 H NMR and X-ray crystallography of [Os( p -cym)( N,N -AZBTZ-NMe2 )Cl]PF6 ( 1a ), [Os( p -cym)( N,N -AZBTZ-NMe2 )Br]PF6 ( 2a ), [Os( p -cym)( N,C -AZBTZ-NMe2 )Br] ( 2b ), and [Os( p -cym)( N,C -AZBTZ-NMe2 )I] ( 3b )...
November 27, 2017: Organometallics
Patrick R Melvin, Ainara Nova, David Balcells, Nilay Hazari, Mats Tilset
Aryl sulfamates are valuable electrophiles for cross-coupling reactions because they can easily be synthesized from phenols and can act as directing groups for C-H bond functionalization prior to cross-coupling. Recently, it was demonstrated that (1-t Bu-Indenyl)Pd(XPhos)Cl (XPhos = 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl) is a highly active precatalyst for room-temperature Suzuki-Miyaura couplings of a variety of aryl sulfamates. Herein, we report an in-depth computational investigation into the mechanism of Suzuki-Miyaura reactions with aryl sulfamates using an XPhos-ligated palladium catalyst...
September 25, 2017: Organometallics
Samantha Lau, Bryan Ward, Xueer Zhou, Andrew J P White, Ian J Casely, Stuart A Macgregor, Mark R Crimmin
The isolable ruthenium(II) bis(dinitrogen) complex [Ru(H)2 (N2 )2 (PCy3 )2 ] ( 1 ) reacts with aryl ethers (Ar-OR, R = Me and Ar) containing a ketone directing group to effect sp2 C-O bond activation at temperatures below 40 °C. DFT studies support a low-energy Ru(II)/Ru(IV) pathway for C-O bond activation: oxidative addition of the C-O bond to Ru(II) occurs in an asynchronous manner with Ru-C bond formation preceding C-O bond breaking. Alternative pathways based on a Ru(0)/Ru(II) couple are competitive but less accessible due to the high energy of the Ru(0) precursors...
September 25, 2017: Organometallics
Xin Yu, Chen-Ho Tung, Wenguang Wang, Mioy T Huynh, Danielle L Gray, Sharon Hammes-Schiffer, Thomas B Rauchfuss
This study describes the structural, spectroscopic, and electrochemical properties of electronically unsymmetrical diiron hydrides. The terminal hydride Cp*Fe(pdt)Fe(dppe)(CO)H ([ 1 ( t -H)]0 , Cp*- = Me5 C5 - , pdt2- = CH2 (CH2 S- )2 , dppe = Ph2 PC2 H4 PPh2 ) was prepared by hydride reduction of [Cp*Fe(pdt)Fe(dppe)(CO)(NCMe)]+ . As established by X-ray crystallography, [ 1 ( t -H)]0 features a terminal hydride ligand. Unlike previous examples of terminal diiron hydrides, [ 1 ( t -H)]0 does not isomerize to the bridging hydride [ 1 ( μ -H)]0 ...
June 12, 2017: Organometallics
Noémie Lalaoui, Toby Woods, Thomas B Rauchfuss, Giuseppe Zampella
The azadithiolate complex Fe2 [(SCH2 )26 NMe](CO)6 reacts with borane to give an initial 1:1 adduct, which spontaneously decarbonylates to give Fe2 [(SCH2 )2 NMeBH3 ](CO)5 . Featuring a Fe-H-B three-center, two-electron interaction, the pentacarbonyl complex is a structural model for H2 complexes invoked in the [FeFe]-hydrogenases. The pentacarbonyl compound is a " σ complex", where a B-H σ bond serves as a ligand for iron. The structure of this σ complex was characterized by variable-temperature NMR spectroscopy and X-ray crystallography...
June 12, 2017: Organometallics
Eric M Lewandowski, Łukasz Szczupak, Stephanie Wong, Joanna Skiba, Adam Guśpiel, Jolanta Solecka, Valerije Vrček, Konrad Kowalski, Yu Chen
A series of six novel metallocenyl-7-ADCA (metallocenyl = ferrocenyl or ruthenocenyl; 7-ADCA = 7-aminodesacetoxycephalosporanic acid) conjugates were synthesized and their antibacterial properties evaluated by biochemical and microbiological assays. The ruthenocene derivatives showed a higher level of inhibition of DD-carboxypeptidase 64-575, a Penicillin Binding Protein (PBP), than the ferrocene derivatives and the reference compound penicillin G. Protein X-ray crystallographic analysis revealed a covalent acyl-enzyme complex of a ruthenocenyl compound with CTX-M β-lactamase E166A mutant, corresponding to a similar complex with PBPs responsible for the bactericidal activities of these compounds...
May 8, 2017: Organometallics
Sandra Y de Boer, Ties J Korstanje, Stefan R La Rooij, Rogier Kox, Joost N H Reek, Jarl Ivar van der Vlugt
The novel tridentate PNNOH pincer ligand L H features a reactive 2-hydroxypyridine functionality as well as a bipyridyl-methylphosphine skeleton for meridional coordination. This proton-responsive ligand coordinates in a straightforward manner to RuCl(CO)(H)(PPh3 )3 to generate complex 1 . The methoxy-protected analogue L Me was also coordinated to Ru(II) for comparison. Both species have been crystallographically characterized. Site-selective deprotonation of the 2-hydroxypyridine functionality to give 1' was achieved using both mild (DBU) and strong bases (KOt Bu and KHMDS), with no sign of involvement of the phosphinomethyl side arm that was previously established as the reactive fragment...
April 24, 2017: Organometallics
Xin Yi See, Evan P Beaumier, Zachary W Davis-Gilbert, Peter L Dunn, Jacob A Larsen, Adam J Pearce, T Alex Wheeler, Ian A Tonks
Low-valent TiII species have typically been synthesized by the reaction of TiIV halides with strong metal reductants. Herein we report that TiII species can be generated simply by reacting TiIV imido complexes with 2 equiv of alkyne, yielding a metallacycle that can reductively eliminate pyrrole while liberating TiII . In order to probe the generality of this process, TiII -catalyzed alkyne trimerization reactions were carried out with a diverse range of TiIV precatalysts.
April 10, 2017: Organometallics
Mohammad Aghazadeh Meshgi, Rainer Zitz, Małgorzata Walewska, Judith Baumgartner, Christoph Marschner
Most known silatrane chemistry is concerned with examples where the attached silatrane substituent atom is that of an element more electronegative than silicon. The current study features silylated silatranes with a range of electropositive elements attached to the silyl group. The resulting compounds show different degrees of electron density on the silatrane-substituted silicon atom. This directly affects the Si-N interaction of the silatrane which can be monitored either by (29)Si NMR spectroscopy or directly by single crystal XRD analysis of the Si-N distance...
April 10, 2017: Organometallics
Isabelle Chambrier, Dragoş-Adrian Roşca, Julio Fernandez-Cestau, David L Hughes, Peter H M Budzelaar, Manfred Bochmann
The gold(III) methoxide complex (C(∧)N(∧)C)AuOMe (1) reacts with tris(p-tolyl)phosphine in benzene at room temperature under O abstraction to give the methylgold product (C(∧)N(∧)C)AuMe (2) together with O=P(p-tol)3 ((C(∧)N(∧)C) = [2,6-(C6H3(t) Bu-4)2pyridine](2-)). Calculations show that this reaction is energetically favorable (ΔG = -32.3 kcal mol(-1)). The side products in this reaction, the Au(II) complex [Au(C(∧)N(∧)C)]2 (3) and the phosphorane (p-tol)3P(OMe)2, suggest that at least two reaction pathways may operate, including one involving (C(∧)N(∧)C)Au(•) radicals...
April 10, 2017: Organometallics
Sopheavy Siek, Dalton B Burks, Deidra L Gerlach, Guangchao Liang, Jamie M Tesh, Courtney R Thompson, Fengrui Qu, Jennifer E Shankwitz, Robert M Vasquez, Nicole Chambers, Gregory J Szulczewski, Douglas B Grotjahn, Charles Edwin Webster, Elizabeth T Papish
Hydrogenation reactions can be used to store energy in chemical bonds, and if these reactions are reversible, that energy can be released on demand. Some of the most effective transition metal catalysts for CO2 hydrogenation have featured pyridin-2-ol-based ligands (e.g., 6,6'-dihydroxybipyridine (6,6'-dhbp)) for both their proton-responsive features and for metal-ligand bifunctional catalysis. We aimed to compare bidentate pyridin-2-ol based ligands with a new scaffold featuring an N -heterocyclic carbene (NHC) bound to pyridin-2-ol...
March 27, 2017: Organometallics
Mark K Rong, Koen van Duin, Tom van Dijk, Jeroen J M de Pater, Berth-Jan Deelman, Martin Nieger, A W Ehlers, J Chris Slootweg, Koop Lammertsma
Highly stable iminophosphanes, obtained from alkylating nitriles and reaction of the resulting nitrilium ions with secondary phosphanes, were explored as tunable P-monodentate and 1,3-P,N bidentate ligands in rhodium complexes. X-ray crystal structures are reported for both κ(1) and κ(2) complexes with the counterion in one of them being an unusual anionic coordination polymer of silver triflate. The iminophosphane-based ruthenium(II)-catalyzed hydration of benzonitrile in 1,2-dimethoxyethane (180 °C, 3 h) and water (100 °C, 24 h) and under solvent free conditions (180 °C, 3 h) results in all cases in the selective formation of benzamide with yields of up to 96%, thereby outperforming by far the reactions in which the common 2-pyridyldiphenylphosphane is used as the 1,3-P,N ligand...
March 13, 2017: Organometallics
Matthew C Leclerc, Bulat M Gabidullin, Jason G Da Gama, Stephanie L Daifuku, Theresa E Iannuzzi, Michael L Neidig, R Tom Baker
Herein, a recently reported polyfluoroalkenyl imidazolium salt is shown to react with nitrogen-, oxygen- and sulfur-based nucleophiles at the C β position in a stereoselective and regioselective fashion, without the use of a transition metal. In contrast, reactivity with 1-methylimidazole demonstrates net substitution at C α . This product reacts quantitatively with water, affording clean transformation of a difluoromethylene group to give an α , β -unsaturated trifluoromethyl ketone. Further reactivity studies demonstrate that the difluoromethyl fragment of an N-heterocyclic fluoroalkene is capable of direct C-C bond formation with NaCp through loss of sodium fluoride and double C-F bond activation (Cp = cyclopentadienide)...
February 27, 2017: Organometallics
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