Copper(II) Activation of Nitrite: Nitrosation of Nucleophiles and Generation of NO by Thiols

Nitrite (NO₂^–) and nitroso compounds (E-NO, E = RS, RO, and R₂N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper­(II) nitrito complex [Cl₂NN_F6]­Cu­(κ²-O₂N)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu^II]­(κ²-O₂N) that leads to <i>S</i>-nitrosation to give the <i>S</i>-nitrosothiol RSNO and copper­(II) hydroxide [Cu^II]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph₂NH and alcohol ^tBuOH to give Ph₂NNO and ^tBuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper­(II) thiolate [Cu^II]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu^II]-OH

Copper(II) Activation of Nitrite: Nitrosation of Nucleophiles and Generation of NO by Thiols

Nitrite (NO₂^–) and nitroso compounds (E-NO, E = RS, RO, and R₂N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper­(II) nitrito complex [Cl₂NN_F6]­Cu­(κ²-O₂N)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu^II]­(κ²-O₂N) that leads to <i>S</i>-nitrosation to give the <i>S</i>-nitrosothiol RSNO and copper­(II) hydroxide [Cu^II]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph₂NH and alcohol ^tBuOH to give Ph₂NNO and ^tBuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper­(II) thiolate [Cu^II]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu^II]-OH

Copper(II) Activation of Nitrite: Nitrosation of Nucleophiles and Generation of NO by Thiols

Nitrite (NO₂^–) and nitroso compounds (E-NO, E = RS, RO, and R₂N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper­(II) nitrito complex [Cl₂NN_F6]­Cu­(κ²-O₂N)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu^II]­(κ²-O₂N) that leads to <i>S</i>-nitrosation to give the <i>S</i>-nitrosothiol RSNO and copper­(II) hydroxide [Cu^II]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph₂NH and alcohol ^tBuOH to give Ph₂NNO and ^tBuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper­(II) thiolate [Cu^II]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu^II]-OH

Copper(II) Activation of Nitrite: Nitrosation of Nucleophiles and Generation of NO by Thiols

Nitrite (NO₂^–) and nitroso compounds (E-NO, E = RS, RO, and R₂N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper­(II) nitrito complex [Cl₂NN_F6]­Cu­(κ²-O₂N)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu^II]­(κ²-O₂N) that leads to <i>S</i>-nitrosation to give the <i>S</i>-nitrosothiol RSNO and copper­(II) hydroxide [Cu^II]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph₂NH and alcohol ^tBuOH to give Ph₂NNO and ^tBuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper­(II) thiolate [Cu^II]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu^II]-OH

Copper(II) Activation of Nitrite: Nitrosation of Nucleophiles and Generation of NO by Thiols

Nitrite (NO₂^–) and nitroso compounds (E-NO, E = RS, RO, and R₂N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper­(II) nitrito complex [Cl₂NN_F6]­Cu­(κ²-O₂N)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu^II]­(κ²-O₂N) that leads to <i>S</i>-nitrosation to give the <i>S</i>-nitrosothiol RSNO and copper­(II) hydroxide [Cu^II]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph₂NH and alcohol ^tBuOH to give Ph₂NNO and ^tBuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper­(II) thiolate [Cu^II]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu^II]-OH

Facile C–H, C–F, C–Cl, and C–C Activation by Oxatitanacyclobutene Complexes

Aryl ketones react readily with oxatitanacyclobutenes bearing pentamethylcyclopentadienyl ligands to form unique titanocene complexes resulting from Cp* modification and C–H activation. An intermediate in this reaction is intercepted with various functional groups to form carbonyl insertion, C–F activation, and cyclopropane ring-opening products

El Diario de Pontevedra : periódico liberal: Ano XXVII Número 7742 - 1910 marzo 1

Copper­(II) aryl species are proposed key intermediates in Cu-catalyzed cross-coupling reactions. Novel three-coordinate copper­(II) aryls [Cu^II]-C₆F₅ supported by ancillary β-diketiminate ligands form in reactions between copper­(II) alkoxides [Cu^II]-O^<i>t</i>Bu and B­(C₆F₅)₃. Crystallographic, spectroscopic, and DFT studies reveal geometric and electronic structures of these Cu­(II) organometallic complexes. Reaction of [Cu^II]-C₆F₅ with the free radical NO_(g) results in C-N bond formation to give [Cu]­(η²-ONC₆F₅). Remarkably, addition of the phenolate anion PhO^– to [Cu^II]-C₆F₅ directly affords diaryl ether PhO-C₆F₅ with concomitant generation of the copper­(I) species [Cu^I]­(solvent) and {[Cu^I]-C₆F₅}⁻. Experimental and computational analysis supports redox disproportionation between [Cu^II]-C₆F₅ and {[Cu^II]­(C₆F₅)­(OPh)}⁻ to give {[Cu^I]-C₆F₅}⁻ and [Cu^III]­(C₆F₅)­(OPh) unstable toward reductive elimination to [Cu^I]­(solvent) and PhO-C₆F₅

Quantitative Analysis of Different Formation Modes of Platinum Nanocrystals Controlled by Ligand Chemistry

Well-defined metal nanocrystals play important roles in various fields, such as catalysis, medicine, and nanotechnology. They are often synthesized through kinetically controlled process in colloidal systems that contain metal precursors and surfactant molecules. The chemical functionality of surfactants as coordinating ligands to metal ions however remains a largely unsolved problem in this process. Understanding the metal–ligand complexation and its effect on formation kinetics at the molecular level is challenging but essential to the synthesis design of colloidal nanocrystals. Herein we report that spontaneous ligand replacement and anion exchange control the form of coordinated Pt–ligand intermediates in the system of platinum acetylacetonate [Pt­(acac)₂], primary aliphatic amine, and carboxylic acid ligands. The formed intermediates govern the formation mode of Pt nanocrystals, leading to either a pseudo two-step or a one-step mechanism by switching on or off an autocatalytic surface growth. This finding shows the importance of metal–ligand complexation at the prenucleation stage and represents a critical step forward for the designed synthesis of nanocrystal-based materials

Uranium(IV) Chloride Complexes: UCl₆^2– and an Unprecedented U(H₂O)₄Cl₄ Structural Unit

The room temperature synthesis and structural characterization of two U­(IV) compounds isolated from acidic aqueous solution is reported. Evaporation of a U­(IV)/HCl solution containing pyridinium (HPy) yielded (HPy)₂UCl₆ (<b>1</b>), yet in the presence of an organic carboxylate U­(H₂O)₄Cl₄­·(HPy·Cl)₂ (<b>2</b>) is obtained. The structures have been determined by single crystal X-ray diffraction and characterized by Raman, IR, and optical spectroscopies. The magnetism of both compounds was also investigated. The structure of <b>1</b> is built from UCl₆^2– anionic units, pervasive in descriptions of the aqueous chemistry of tetravalent uranium, and is found to undergo a phase transition from <i>C</i>2/<i>m</i> to <i>P</i>1̅ upon cooling. By comparison, the structure of <b>2</b> contains a neutral U­(IV)-aquo-chloro complex, U­(H₂O)₄Cl₄, for which there is no literature precedence. Density functional theory calculations were performed to predict the geometries, vibrational frequencies, and relative energetics of the UCl₆^2– and U­(H₂O)₄Cl₄ units. The energetics of the reaction of U­(H₂O)₄Cl₄ to form the dianion are predicted to be exothermic in the gas phase and in aqueous solution. The predicted energetics coupled with no previous solid state reports of a U­(IV)-aquo-chloro complex may point toward the importance of hydrogen bonding and other supramolecular interactions, prevalent in the structures of <b>1</b> and <b>2</b>, on the stabilization and/or crystallization of the U­(H₂O)₄Cl₄ structural unit

Mechanism of H₂ Production by Models for the [NiFe]-Hydrogenases: Role of Reduced Hydrides

The intermediacy of a reduced nickel–iron hydride in hydrogen evolution catalyzed by Ni–Fe complexes was verified experimentally and computationally. In addition to catalyzing hydrogen evolution, the highly basic and bulky (dppv)­Ni­(μ-pdt)­Fe­(CO)­(dppv) ([<b>1</b>]⁰; dppv = <i>cis</i>-C₂H₂­(PPh₂)₂) and its hydride derivatives have yielded to detailed characterization in terms of spectroscopy, bonding, and reactivity. The protonation of [<b>1</b>]⁰ initially produces <i>unsym</i>-[H<b>1</b>]⁺, which converts by a first-order pathway to <i>sym</i>-[H<b>1</b>]⁺. These species have <i>C</i>₁ (unsym) and <i>C</i>_<i>s</i> (sym) symmetries, respectively, depending on the stereochemistry of the octahedral Fe site. Both experimental and computational studies show that [H<b>1</b>]⁺ protonates at sulfur. The <i>S</i> = 1/2 hydride [H<b>1</b>]⁰ was generated by reduction of [H<b>1</b>]⁺ with Cp*₂Co. Density functional theory (DFT) calculations indicate that [H<b>1</b>]⁰ is best described as a Ni­(I)–Fe­(II) derivative with significant spin density on Ni and some delocalization on S and Fe. EPR spectroscopy reveals both kinetic and thermodynamic isomers of [H<b>1</b>]⁰. Whereas [H<b>1</b>]⁺ does not evolve H₂ upon protonation, treatment of [H<b>1</b>]⁰ with acids gives H₂. The redox state of the “remote” metal (Ni) modulates the hydridic character of the Fe­(II)–H center. As supported by DFT calculations, H₂ evolution proceeds either directly from [H<b>1</b>]⁰ and external acid or from protonation of the Fe–H bond in [H<b>1</b>]⁰ to give a labile dihydrogen complex. Stoichiometric tests indicate that protonation-induced hydrogen evolution from [H<b>1</b>]⁰ initially produces [<b>1</b>]⁺, which is reduced by [H<b>1</b>]⁰. Our results reconcile the required reductive activation of a metal hydride and the resistance of metal hydrides toward reduction. This dichotomy is resolved by reduction of the remote (non-hydride) metal of the bimetallic unit