I. K. Gregor

Application of secondary-electron capture negative-ion (SECNI) mass spectrometry to the analysis of metal-organic compounds.

The application of secondary-electron capture negative-ion (SECNI) mass spectrometry to the analysis of metal-organic compounds is described and typical examples are discussed. Negative-ion mass spectra are simple, molecular anions and ligand ions being the predominant species. Metallic or ligand impurities are readily identified by this technique, which makes it extremely useful for the determination of purity and formulation of metal-organic compounds. Because of its sensitivity, the technique is also valuable for trace metal analysis.

Gas phase ion molecule reactions of organometallic compounds; protonation of selected η6-arenetricarbonylchromium complexes and η6-cycloheptatriene complexes of the Group VI metals with various Brønsted acid reagent ions

Abstract η 6 -Arenetricarbonylchromium(0) complexes, (with the η 6 -arene = benzene, toluene, methylbenzoate and acetophenone) and η 6 -cycloheptatrienetricarbonyl complexes of chromium(0), molybdenum(0) and tungsten(0) undergo reactions in the gas phase with the Bronsted acid reagent ions H 3 + , CH 5 + , t-C 4 H 9 + , (NH 3 ) n H + which depend on the Bronsted acid strengths of these ions and also on the basicity of the metal complexes. Processes which involve either metal or ligand proton attachment, as well as charge exchange, electrophillic addition and rearrangement reactions have been identified. Some comparisons are drawn between these gas phase observations and the solutions phase behaviour of these compounds.

Gas phase electron attachment reactions and negative ion mass spectra of substituted pentafluorophenyl compounds

Abstract Compounds of the type C 6 F 5 ·R (R = F, CH 3 , NH 2 , OH, SH, OCH 3 , COCH 3 , CHO, NO 2 , CN) undergo low energy electron attachment reactions in the gas phase under negative chemical ionisation (NCI) conditions which can result in the production of intense negative ion beams. Long-lived molecular negative ions are formed when R is highly electron withdrawing and this correlates in certain cases (R = F, CN, CHO) with reported [M] − · autodetachment times. Compounds with R = COCH 3 , CHO, CN which exhibit minimal fragmentation of [M] − · are useful negative ion mass calibrants.

Fourier transform ion cyclotron resonance spectroscopic studies of the chemistry of electron deficient organometallic anions: the reactions of [Cr(CO)3− with alkenes and polyenes

Abstract Reactions of the radical anion [Cr(CO) 3 ] − with a series of alkenes and polyenes in the gas phase have been examined. With straight chain alkenes the dehydrogenated main ionic product was [C n H 2 n -2 Cr(CO) 3 ] − and the minor product [C n -H 2 n -2 Cr(CO) 2 ] ??? , for n = 4–8, and the reactions giving these are suggested to involved η 4 -conjugated alkadiene interactions with the metal centre. Similar reactions took place with the cyclic alkene C 6 H 10 and its methyl-substituted analogue C 4 H 12 . In contrast vinylbenzene, C 8 H 8 , and propene gave only the decarbonylated ionic products [C 8 H 8 Cr(CO) 2 ] − and [C 3 H 6 Cr(CO)] − , respectively. Isomeric 1,3- and 1,4-cyclohexadienes gave the decarbonylated dehydrogenated products, [C 6 H 6 Cr(CO) 2 ] − , whereas the polyenes gave the ionic species [(Polyene)Cr(CO) x ] − with x = 0–3.

Gas phase ion-molecule reactions of organometallic compounds; protonation of η4-dienetricarbonyliron and η4-polyenetricarbonyliron complexes by various brønsted acid reagent ions

Gas phase protonation reactions have been investigated between a series of Bronsted acid reagent ions, viz.: H3+, CH5+, t-C4H9+, (NH3)nH+, and various η4-dienetricarbonyliron and η4-polyenetricarbonyliron compounds. The protonation reactions and mass spectra are discussed in terms of the relative acid strengths of the protonating reagent ions, and comparisons are drawn between these gas phase results and the conditions necessary to effect protonation of these and similar organometallic compounds in the solution phase.

Gas phase molecular anion formation by η4- and η6-cycloheptatriene derivatives of zerovalent iron, chromiun, molybdenum, and tungsten tricarbonyls

Abstract The title compounds form molecular anions in high abundance in their negative ion mass spectra in apparent violation of the rare-gas rule.

Gas phase oxidative-addition reactions of alkyl radicals at complexed cobalt(II) centres

Abstract Negative chemical ionisation mass spectrometry is used as a probe to identify reactions between hydrocarbon radicals and cornplexed cobalt(II) centres in the gas phase. Methane NCI mass spectra of a series of cobalt(II) complexes containing O4, O2N2 and N4 donor atom sets are characterised by adduct ions of the form [M + CnH2n+1]− at m/z values above the molecular ion, [M]−. Formation of such ionic species has been rationalised in terms of a one-electron oxidative-addition mechanism involving attack by hydrocarbon plasma-derived alkyl radicals at the metal centre prior to electron capture: CoIILn + R• → RCoIIILn e − [CoILn]−. The competing resonance electron attachment reaction: CoIILn e − also occurs within the ion source.

Chemistry of coordinatively unsaturated and electron deficient carbonyl metallate ions. Gas phase reactions of [Fe(CO)2]- with hydrocarbons

The gas phase reactions of the metal dicarbonyl anion Fe(CO)2− with fifteen isotopically unlabelled, D- and 13C-labelled C2–6 alcohols have been studied by the use of Fourier transform ion cyclotron resonance mass spectroscopy. Several competitive reaction channels which are related to the structures of the alcohols as well as their carbon content have been identified for these systems. For the primary alcohols, separate decarbonylation and dehydrogenation channels along with a channel involving CH and OH bond activations to give Fe(CO)3− as an end product have been identified. With C3–6 primary alcohols the predominant terminal reaction product is one which involved bis-dehydrogenation of a collision complex. For secondary alcohols, no Fe(CO)3− product ions were detected and the dominant reaction channel was one which resulted in bis-dehydrogenation of a collision complex. With tertiary alcohols, ROH, the major ionic and dehydrogenated product was of the type [(CO)2Fe(ORH)]−.

Chemistry of electron deficient organometallic anions: gas phase reactions of [Cr(CO)3]−· with amines

On donne les distributions des produits ioniques pour les reactions de [Cr(CO) 3 ] ÷ avec les amines

Gas-phase chemistry of first transition series carbonyl metallate ions: reactions with 13C-labelled carbonyl sulfide

Abstract Fourier transform ion cyclotron resonance (FTICR) spectroscopic methods have been applied to examine the gas phase reactions of the metal carbonyl anions [metal(CO) 4 ] − , metalCr, Mn; [metal(CO) 3 ] − , metalCr, Mn, Fe; and [metal(CO) 2 ] − , metalFe, Ni with 13 C-labelled carbonyl sulfide. Measurements of temporal variations of ionic product distributions have allowed mechanisms to be proposed to account for the formation of both carbonylated and decarbonylated metal-S bonded ionic reaction products which derive from 13 CS cleavages in [(CO) x ·metal·η 2 -S 13 CO] − intermediates.