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Léon Witteman, Cody B van Beek, Oscar N van Veenhuizen, Martin Lutz, Marc-Etienne Moret
The tris-N-heterocycle germanide (tmim)Ge- ( 1 ) (tmimH3 = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim3- trianion on GeCl2 ·dioxane. In combination with the previously reported (tmim)Si- and (tmim)P analogues, it provides a convenient model for investigating the influence of the central atom on the properties of isoelectronic ligands. Complexation of the germanide (tmim)Ge- to CuCl resulted in the dimeric chloro cuprate [(tmim)GeCu(μ-Cl)]2 2- , which is prone to dissociation in MeCN to form the neutral, solvated germylcopper (tmim)GeCu(NCMe)3 ...
January 28, 2019: Organometallics
Jonathan Gordon, Sven Hildebrandt, Kendra R Dewese, Sven Klare, Andreas Gansäuer, T V RajanBabu, William A Nugent
The role of Cp2 Ti(H)Cl in the reactions of Cp2 TiCl with trisubstituted epoxides has been investigated in a combined experimental and computational study. Although Cp2 Ti(H)Cl has generally been regarded as a robust species, its decomposition to Cp2 TiCl and molecular hydrogen was found to be exothermic (ΔG = -11 kcal/mol when the effects of THF solvation are considered). In laboratory studies, Cp2 Ti(H)Cl was generated using the reaction of 1,2-epoxy-1-methylcyclohexane with Cp2 TiCl as a model. Rapid evolution of hydrogen gas was demonstrated, indicating that Cp2 Ti(H)Cl is indeed a thermally unstable molecule, which undergoes intermolecular reductive elimination of hydrogen under the reaction conditions...
December 24, 2018: Organometallics
Yiming Zhao, Huy van Nguyen, Louise Male, Philip Craven, Benjamin R Buckley, John S Fossey
Twelve 1,5-disubtituted and fourteen 5-substituted 1,2,3-triazole derivatives bearing diaryl or dialkyl phosphines at the 5-position were synthesized and used as ligands for palladium-catalyzed Suzuki-Miyaura cross-coupling reactions. Bulky substrates were tested, and lead-like product formation was demonstrated. The online tool SambVca2.0 was used to assess steric parameters of ligands and preliminary buried volume determination using XRD-obtained data in a small number of cases proved to be informative. Two modeling approaches were compared for the determination of the buried volume of ligands where XRD data was not available...
November 26, 2018: Organometallics
Matthew R Gyton, Baptiste Leforestier, Adrian B Chaplin
The synthesis and characterization of five-coordinate rhodium(III) and iridium(III) 2,2'-biphenyl complexes [M(CNC-12)(biph)][BArF 4 ] (M = Rh ( 1a ), Ir ( 1b )), featuring the macrocyclic lutidine- and NHC-based pincer ligand CNC-12 are reported. In the solid state these complexes are notable for the adoption of weak ε-agostic interactions that are characterized by M ···H- C contacts of ca. 3.0 Å by X-ray crystallography and ν(CH) bands of reduced wavenumber by ATR IR spectroscopy. Remarkably, these interactions persist on dissolution and were observed at room temperature using NMR spectroscopy (CD2 Cl2 ) and solution-phase IR spectroscopy (CCl4 )...
November 12, 2018: Organometallics
Salvador B Muñoz, Valerie E Fleischauer, William W Brennessel, Michael L Neidig
Iron and N -heterocyclic carbenes (NHCs) have proven to be a successful pair in catalysis, with reactivity and selectivity being highly dependent on the nature of the NHC ligand backbone saturation and N -substituents. Four (NHC)Fe(1,3-dioxan-2-ylethyl)2 complexes have been isolated and spectroscopically characterized to correlate their reactivity to steric effects of the NHC from both the backbone saturation and N -substituents. Only in the extreme case of SIPr where NHC backbone and N -substituent steric effects are the largest is there a major structural perturbation observed crystallographically...
September 24, 2018: Organometallics
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
Sudarsan VenkatRamami, Richard R Schrock, Amir Hoveyda, Peter Müller, Charlene Tsay
Reactions between Z -XCH=CHX where X = Cl, CF3 , or CN and Mo(N- t -Bu)(CH- t -Bu)(OHIPT)Cl(PPh2 Me) (OHIPT = O-2,6-(2,4,6- i -Pr3 C6 H2 )2 C6 H3 ) produce Mo(N- t -Bu)(CHX)(OHIPT)Cl(PPh2 Me) complexes. Addition of 2,2'-bipyridyl (Bipy) yields Mo(N- t -Bu)(CHX)(OHIPT)Cl(Bipy) complexes, which could be isolated and structurally characterized. The reaction between Mo(N- t -Bu)(CH- t -Bu)(OHMT)Cl(PPh2 Me) (OHMT = O-2,6-(2,4,6-Me3 C6 H2 )2 C6 H3 ) and Z -ClCH=CHCl in the presence of Bipy produces a mixture that contains both Mo(N- t -Bu)(CHCl)(OHMT)Cl(PPh2 Me) and Mo(N- t -Bu)(CHCl)(OHMT)Cl(Bipy), but the relatively insoluble product that crystallizes from toluene- d 8 is the phosphoniomethylidene complex, [Mo(N- t -Bu)(CHPPh2 Me)(OHMT)(Cl)(Bipy)]Cl...
June 11, 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
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