Crystal structure of bis(acetylacetonato-κ2O,O′)(tetrahydrofuran-κO)(trifluoromethanesulfonato-κO)iron(III)

The mononuclear title complex, [Fe(CF3O3S)(C5H7O2)2(C4H8O)] or [Fe(acac)2(OTf)(THF)] (acac = acetylacetonate; OTf = trifluoromethanesulfonate; THF = tetrahydrofuran), (I), consists of one six-coordinate Fe3+ atom in a slightly distorted octahedral environment [Fe—O bond-length range = 1.9517 (11)–2.0781 (11) Å]. The triflate ligand was found to be disordered over two sets of sites, with a site-occupancy ratio of 0.622 (16):0.378 (16). Weak intermolecular C—H...O and C—H...F hydrogen-bonding interactions generate a two-dimensional supramolecular structure lying parallel to (100). This is only the second crystal structure reported of a mononuclear bis(acetylacetonato)iron(III) complex

Crystal structure of 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene

The crystal structure of the well-studied 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene molecule, C20H12S4, (I), also known as exTTF, is reported. The molecular structure of (I) consists of a dihydroanthracene moiety with two 1,3-dithiol-2-ylidene substituents. This is a saddle-shaped molecule, which interacts with a close neighbor through various π–π and C—H...π contacts to form a `dimer'. These `dimers' interact through a series of C—H...S and C—H...π contacts to construct a complex three-dimensional extended structure

Nitrite-Phenol-NO Crosstalk: Phenol Oxidation and NO Generation from Nitrite at Copper(II) Sites

Nitrite is involved in a plethora of biological phenomena that includes tyrosine nitration associated with neurodegenerative disorders and gastric phenol metabolism. Reaction of the b-diketiminato model complex [Cl2NNF6]Cu(k2-O2N) with phenols outlines the coupled generation of NO with phenol oxidation by nitrite at copper(II). Kinetic studies support nucleophilic attack of the hydroxyl group of phenols ArOH on the bound nitrite in [CuII](k2-O2N) to give the copper(II) hydroxide [CuII]-OH along with the O-nitrosated phenol ArONO that ultimately leads to the corresponding biphenol or o-nitrophenol. The especially electron-rich antioxidant a-tocapherol (vitamin E) quickly generates NO upon interaction with [CuII](k2-O2N). X-ray analysis of the oxidation products of the a-tocapherol analogue PMC reveal formation of an elusive O-quinone methide bound to [CuI], revealing two electron oxidation of PMC by [CuII](k2-O2N). These studies illustrate anaerobic pathways that generate NO from nitrite at copper(II) sites that result in phenol oxidation

Tris(pyrazolyl)borate Copper Hydroxide Complexes Featuring Tunable Intramolecular H-bonding

A modular synthesis provides access to a series of new tris(pyrazolyl)borate ligands XpyMeTpK that possess a single functionalized pendant pyridyl (py) or pyrimidyl (pyd) arm designed to engage in tunable intramolecular H-bonding to metal–bound functionalities. To illustrate such H-bonding interactions, a series of [XpyMeTpCu]2(–OH)2(6a–6e) complexes were synthesized from the corresponding XpyMeTpCu–OAc (5a–5e) complexes. Single crystal X-ray structures of three new dinuclear [XpyMeTpCu]2(–OH)2complexes reveal H-bonding between the pendant heterocycle and bridging hydroxide ligands while the donor arm engages the copper center in an unusual monomeric DMAPMeTpCu–OH complex. Vibrational studies (IR) of each bridging hydroxide complex reveal reduced OH frequencies that tracks with the H-bond accepting ability of the pendant arm

Crystal structure of 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene

The crystal structure of the well-studied 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene molecule, C20H12S4, (I), also known as exTTF, is reported. The molecular structure of (I) consists of a dihydroanthracene moiety with two 1,3-dithiol-2-ylidene substituents. This is a saddle-shaped molecule, which interacts with a close neighbor through various π-π and C - H⋯π contacts to form a \u27dimer\u27. These \u27dimers\u27 interact through a series of C - H⋯S and C - H⋯π contacts to construct a complex three-dimensional extended structure

General alkyl fluoride functionalization via short-lived carbocation-organozincate ion pairs

Abstract Fluorinated organic compounds are frequently used across the chemical and life sciences. Although a large, structurally diverse pool of alkyl fluorides is nowadays available, synthetic applications trail behind the widely accepted utility of other halides. We envisioned that C(sp2)-C(sp3) cross-coupling reactions of alkyl fluorides with fluorophilic organozinc compounds should be possible through a heterolytic mechanism that involves short-lived ion pairs and uses the stability of the Zn-F bond as the thermodynamic driving force. This would be mechanistically different from previously reported radical reactions and overcome long-standing limitations of organometallic cross-coupling methodology, including competing β-hydride elimination, homodimerization and hydrodefluorination. Here, we show a practical Csp3-F bond functionalization method that expands the currently restricted synthetic space of unactivated primary, secondary and tertiary C(sp3)-F bonds but also uses benzylic, propargylic and acyl fluorides. Many functional groups and sterically demanding substrates are tolerated, which allows practical carbon-carbon bond formation and late-stage functionalization

Chemical and Electrocatalytic Ammonia Oxidation by Ferrocenium

Recognizing the potential of ammonia to serve as a carbon-free fuel, we describe an electrocatalytic system for the oxidation of ammonia based on ferrocene (Cp2Fe), an inexpensive, robust catalyst utilizing Earth-abundant iron. Ferrocenium (Cp2Fe+), the 1-electron oxidized form of ferrocene, cleanly oxidizes ammonia to generate nitrogen gas (N2) and protons captured by excess ammonia as NH4+ with electrons reducing ferrocenium to ferrocene. This process occurs under electrocatalytic condi-tions to generate N2 with sustained current. Simple modification of ferrocene through sulfonation allows for solubility in liquid ammonia to enable electrocatalysis in highly concentrated, energy dense solutions of ammonia. Kinetic analysis pro-vides mechanistic clues into the oxidation of ammonia by ferrocenium

Radical Capture at Ni(II) Complexes: C-C, C-N, and C-O Bond Formation

The dinuclear b-diketiminato NiIItert-butoxide {[Me3NN]Ni}2(μ-OtBu)2 (2), synthesized from [Me3NN]Ni(2,4-lutidine) (1) and di-tert-butylperoxide, is a versatile precursor for the synthesis of a series of NiIIcomplexes [Me3NN]Ni-FG to illustrate C-C, C-N, and C-O bond formation at NiII via radicals. {[Me3NN]Ni}2(μ-OtBu)2 reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia and phenols to deliver corresponding mono- or dinuclear [Me3NN]Ni-FG species (FG = O2NCH2, R-NH, ArNH, PhC(O)NH, PhC(O)CH2, NH2and OAr). Many of these NiII complexes are capable of capturing the benzylic radical PhCH(•)CH3 to deliver corresponding PhCH(FG)CH3 products featuring C-C, C-N or C-O bonds. DFT studies shed light on the mechanism of these transformations and suggest two competing pathways that depend on the nature of the functional groups. These radical capture reactions at [NiII]-FG complexes outline key C-C, C-N, and C-O bond forming steps and suggest new families of nickel radical relay catalysts.</p

Copper(II) Ketimides in sp3 C-H Amination

Commercialy available benzphenone imine (HN=CPh2) reacts with b-diketiminato copper(II) tert-butoxide complexes [CuII]-OtBu to form isolable copper(II) ketimides [CuII]-N=CPh2. Structural characterization of the three coordinate copper(II) ketimide [Me3NN]Cu-N=CPh2 reveals a short Cu-Nketimide distance (1.700(2) Å) with a nearly linear Cu-N-C linkage (178.9(2)°). Copper(II) ketimides [CuII]-N=CPh2 readily capture alkyl radicals R• (PhCH(•)Me and Cy•) to form the corresponding R-N=CPh2 products that competes with N-N coupling of copper(II) ketimides [CuII]-N=CPh2 to form the azine Ph2C=N-N=CPh2. Copper(II) ketimides [CuII]-N=CAr2 serve as intermediates in catalytic sp3 C-H amination of substrates R-H with ketimines HN=CAr2 and tBuOOtBu as oxidant to form N-alkyl ketimines R-N=CAr2. This protocol enables the use of unactivated sp3 C-H bonds to give R-N=CAr2 products easily converted to primary amines R-NH2 via simple acidic deprotection.</p

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