Tandem Mass Spectrometry of Perfluorocarboxylate Anions: Fragmentation Induced by Reactive Species Formed From Microwave Excited Hydrogen and Water Plasmas.

Rationale: Polyfluoroalkyl substances (PFAS) like perfluorooctanoic acid have persistent environmental and physiological effects. This study investigates the degradation of CFCO (n = 1-7) with neutral radical fragmentation under oxygen attachment dissociation (OAD). Unique fragments absent from collision-induced dissociation (CID) are observed.

The Magnesium Dication and Water Synergistically Promote the Protonolysis of Two of the B-C Bonds in the Tetraphenylborate Anion.

Analytes are sampled from both solution phase and gas-phase environments during the ESI process, and thus, the mass spectrum that is measured can reflect both solution and gas-phase conditions. In the gas-phase regime, ion-molecule reactions can influence the types of ions that are observed. Herein, the synergistic effects of a Lewis acid (Mg) and background water are shown to lead to protonolysis of two of the B-C bonds of the tetraphenylborate ion in the gas phase, giving rise to different ions at different reaction times in ESI-MS/MS experiments in a linear ion trap mass spectrometer.

Methide Affinity Scale: Key Thermodynamic Data Underpinning Catalysis, Organic Synthesis, and Organometallic and Polymer Chemistry.

Methide transfer reactions play important roles in many areas of chemistry, including the Grignard reaction, in the transmetalation steps of metal-catalyzed cross-coupling reactions, and in the generation of cationic metal polymerization catalysts. Methide affinities (MAs) are the key thermodynamic quantity that underpin such reactions, and yet comprehensive methide affinity scales are poorly developed. Here, B3LYP-D3BJ/def2-TZVP calculations are used to calculate the energy changes (MAs) for cations (MeZ → Z + Me), neutrals (MeY → Y + Me), and anions (MeX → X + Me) derived from permethyl species of all group s and p elements.

Electronic and Steric Effects on the Reactivity of Seleniranium Ions with Alkenes in the Gas Phase.

Gas phase ion-molecule reactions between seleniranium ions, R--SeCHCH, and -cyclooctene were used to probe electronic and steric effects of substituents on kinetics and branching ratios. The second-order rate coefficients increased in the order -OMeCH < CH < -BrCH < -CFCH < -NOCH, giving a Hammett plot with = 0.98 and ρ = +1.

Near thermal, selective liberation of hydrogen from formic acid catalysed by copper hydride ate complexes.

A near thermal two-step catalytic cycle for the selective release of hydrogen from formic acid by mononuclear cuprate anions was revealed using multistage mass spectrometry experiments, deuterium labelling and DFT calculations. In gas-phase ion-molecule reactions, mononuclear copper hydride anions [(L)Cu(H)] (where L = H, OCH, BH and CN) were found to react with formic acid (HCOH) to yield [(L)Cu(OCH)] and H. The copper formate anions [(L)Cu(OCH)] can decarboxylate collision-induced dissociation (CID) to reform the copper hydride [(L)Cu(H)], thereby closing the two-step catalytic cycle.

Electrospray Ionization Tandem Mass Spectrometry and DFT Survey of Copper(I) Ate Complexes Containing Coordinated Borohydride Anions.

Copper(I) borohydride ate complexes of the type Cat[XCu(BH)] have been previously postulated as intermediates in the reactions of copper salts with borohydride. Negative ion electrospray ionization of an acetonitrile solution of copper(I) phenylacetylide with a 10-fold excess of sodium borohydride (NaBH) revealed the formation of a diverse range of mononuclear, dinuclear and trinuclear cuprates with different numbers of BH, H and CN ligands, the latter likely being formed by abstraction of CN from the acetonitrile solvent. Collision-induced dissociation was used to examine the fragmentation reactions of the following borohydride containing cuprates: [Cu(H)(BH)], [Cu(BH)], [Cu(BH)(CN)], [Cu(H)(BH)], [Cu(H)(BH)], [Cu(BH)(CN)], [Cu(H)(BH)(CN)], [Cu(H)(BH)], [Cu(H)(BH)], [Cu(H)(BH)], [Cu(BH)(CN)], and [Cu(H)(BH)(CN)].

Ion-pairs as a gateway to transmetalation: aryl transfer from boron to nickel and magnesium.

Gas-phase ion-ion reactions between tris-1,10-phenantholine metal dications, [(phen)M] (where M = Ni and Mg), and the tetraphenylborate anion yield the ion-pairs {[(phen)M][BPh]}. The ion-pairs undergo transmetalation upon loss of a phen ligand to give the organometallic complexes [(phen)M(Ph)]. DFT calculations, used to determine the energy barriers for the transmetalation reactions and the hydrolysis reactions, are entirely consistent with the experimental results.

Experimental and theoretical investigations into the mechanisms of haliranium ion π-ligand exchange reactions with cyclic alkenes in the gas phase.

Haliranium ions are intermediates often involved in complex cyclisations, where their structure allows for control over stereospecific outcomes. Extending previous studies into their structure and reactivity in the gas phase, this work focuses on the bimolecular reactivity of ethyl bromiranium and iodiranium ions with cyclic alkenes. The products observed mass spectrometry were broadly attributed to either addition by cyclohexene at the iranium carbon or attack at the heteroatom to undergo associative π-ligand exchange.

Origin of the different reactivity of the high-valent coinage-metal complexes [RCu Me ] and [RAg Me ] (R=allyl).

High-valent tetraalkylcuprates(iii) and -argentates(iii) are key intermediates of copper- and silver-mediated C-C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RM Me ] complexes (M=Cu, Ag and R=allyl) with energy-dependent collision-induced dissociation experiments, advanced quantum-chemical calculations and kinetic computations. The gas-phase fragmentation experiments confirmed the preferred formation of the [RCuMe] anion upon collisional activation of the cuprate(iii) species, consistent with a homo-coupling reaction, whereas the silver analogue primarily yielded [AgMe ] , consistent with a cross-coupling reaction.

Photo-control of bimolecular reactions: reactivity of the long-lived Rhodamine 6G triplet excited state with ˙NO.

Photo-chemistry provides a non-intuitive but very powerful way to probe kinetically limited, sometimes thermodynamically non-favored reactions and, thus, access highly specific products. However, reactivity in the excited state is difficult to characterize directly, due to short lifetimes and challenges in controlling the reaction medium. Among photo-activatable reagents, rhodamine dyes find widespread uses due to a number of favorable properties including their high absorption coefficient.

Phenyl argentate aggregates [AgPh] (n = 2-8): Models for the self-assembly of atom-precise polynuclear organometallics.

Electrospray ionization of phenyl argentates formed by transmetalation reactions between phenyl lithium and silver cyanide provides access to the argentate aggregates, [AgPh], which were individually mass-selected for n = 2-8 in order to generate their gas-phase Ultraviolet Photodissociation (UVPD) "action" spectra over the range 304-399 nm. A strong bathochromic shift in optical spectra was observed with increasing size/n. Theoretical calculations allowed the assignment of the experimental UVPD spectra to specific isomer(s) and provided crucial insights into the transition from the 2D to 3D structure of the metallic component with the increasing size of the complex.

Dissecting transmetalation reactions at the molecular level: C-B versus F-B bond activation in phenyltrifluoroborate silver complexes.

The gas-phase unimolecular reactions of the silver(i) complex [Ag(PhBF)], formed via electrospray ionisation mass spectrometry of solutions containing the phenyltrifluoroborate salt and AgNO, are examined. Upon collision induced dissociation (CID) three major reaction channels were observed for [Ag(PhBF)]: Ph group transfer via a transmetalation reaction to yield [PhAg(PhBF)]; F transfer to produce [FAg(PhBF)]; and release of PhBF. The anionic silver product complexes of these reactions, [LAg(PhBF)] (where L = Ph and F), were then mass-selected and subjected to a further stage of CID.

ORGANOMETALLIC GAS-PHASE ION CHEMISTRY AND CATALYSIS: INSIGHTS INTO THE USE OF METAL CATALYSTS TO PROMOTE SELECTIVITY IN THE REACTIONS OF CARBOXYLIC ACIDS AND THEIR DERIVATIVES.

Carboxylic acids are valuable organic substrates as they are widely available, easy to handle, and exhibit structural and functional variety. While they are used in many standard synthetic protocols, over the past two decades numerous studies have explored new modes of metal-mediated reactivity of carboxylic acids and their derivatives. Mass spectrometry-based studies can provide fundamental mechanistic insights into these new modes of reactivity.

Type IX Secretion System Cargo Proteins Are Glycosylated at the C Terminus with a Novel Linking Sugar of the Wbp/Vim Pathway.

and use the type IX secretion system to secrete cargo proteins to the cell surface where they are anchored via glycolipids. In , the glycolipid is anionic lipopolysaccharide (A-LPS), of partially known structure. Modified cargo proteins were deglycosylated using trifluoromethanesulfonic acid and digested with trypsin or proteinase K.

Using electrospray ionization-tandem mass spectrometry to explore formation and gas-phase chemistry of silver nanoclusters generated from the reaction of silver salts with NaBH in the presence of bis(diphenylarsino)methane.

Electrospray ionization-mass spectrometry (ESI-MS) of mixtures of AgBF or AgNO with the capping ligand bis(diphenylarsino)methane ((Ph As) CH = dpam) in a solution of acetonitrile revealed the formation of the following cations: [Ag(CH CN)(dpam)] , [Ag(dpam) ] , [Ag (Cl)(dpam) ] , and [Ag (Cl) (dpam) ] . Addition of NaBH to these solutions results in the formation of the cluster cations [Ag (BH )(dpam) ] , [Ag (BH )(dpam) ] , [Ag (H)(BH )(dpam) ] , [Ag (BH ) (dpam) ] , [Ag (H)(Cl)(dpam) ] , and [Ag (I)(BH )(dpam) ] , as established by ESI-MS. Use of NaBD confirmed that borohydride is the source of the hydride in these clusters.

Identification of the Side Products That Diminish the Yields of the Monoamidated Product in Metal-Catalyzed C-H Amidation of 2-Phenylpyridine with Arylisocyanates.

The Ru(II)-catalyzed amidation of 2-arylpyridines with aryl isocyanates via C-H bond activation is less efficient than described previously, due to the formation of a series of side products, which were readily identified using direct infusion electrospray mass spectrometry and high-performance liquid chromatography-mass spectrometry.

Photoexcited Pd(ii) auxiliaries enable light-induced control in C(sp)-H bond functionalisation.

Herein we report the photophysical and photochemical properties of palladacycle complexes derived from 8-aminoquinoline ligands, commonly used auxiliaries in C-H activation. Spectroscopic, electrochemical and computational studies reveal that visible light irradiation induces a mixed LLCT/MLCT charge transfer providing access to synthetically relevant Pd(iii)/Pd(iv) redox couples. The Pd(ii) complex undergoes photoinduced electron transfer with alkyl halides generating C(sp)-H halogenation products rather than C-C bond adducts.

Decomposition of protonated ronidazole studied by low-energy and high-energy collision-induced dissociation and density functional theory.

Nitroimidazoles are important compounds in medicine, biology, and the food industry. The growing need for their structural assignment, as well as the need for the development of the detection and screening methods, provides the motivation to understand their fundamental properties and reactivity. Here, we investigated the decomposition of protonated ronidazole [Roni+H] in low-energy and high-energy collision-induced dissociation (CID) experiments.

Experimental and DFT Studies on the Identity Exchange Reactions between Phenyl Chalcogen Iranium Ions and Alkenes.

The gas-phase ion-molecule identity exchange reactions of phenyl chalcogen iranium ions with alkenes have been examined experimentally in a linear ion trap mass spectrometer by isotope labeling experiments. The nature of both the alkene and the chalcogen play crucial roles, with the bimolecular rates for π-ligand exchange following the order: [PhTe(-CH)] + -CD > [PhTe(CD)] + CH > [PhSe(-CH)] + -CD, with no reaction being observed for [PhSe(CD)] + CH, [PhS(CD)] + CH, and [PhS(-CH)] + -CD. The experimental results correlate with RRKM modeling and density functional theory (DFT) calculations, which also demonstrates that these reactions proceed via associative mechanisms.