Reactivity, photochemistry and thermochemistry of simple metal—ligand ions in the gas phase
TL;DR: In this article, the authors discuss recent results from their laboratory on the chemistry, photochemistry and thermodynamics of simple metal-ligand ionic species in the gas phase using laser desorption coupled to Fourier transform mass spectrometry, and successfully generated numerous highly unsaturated metal ions including bare metal carbenes, methyls, hydrides, nitrenes and amides.
About: This article is published in Polyhedron.The article was published on 1988-01-01. It has received 67 citations till now. The article focuses on the topics: Thermochemistry & Reactivity (chemistry).
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TL;DR: In this paper, a detailed account focusing on gas-phase measurements and high quality ab initio calculations that are beginning to explain how metal atom electronic structure determines chemical reactivity is presented.
Abstract: This Account focuses on gas-phase measurements and high quality ab initio calculations that are beginning to explain how metal atom electronic structure determines chemical reactivity The authors have an enormous body of basic chemical reactivity data for M[sup +] and a growing body of data for M[sup 2+] and neutral M Sophisticated experiments can control the kinetic energy and the electronic state of M[sup +] reactants One can study the reactivity of Fe[sup +] in the 3d[sup 6]4s, high-spin ground state, the 3d[sup 7], high-spin first excited state, or the 3d[sup 6]4s, low-spin second excited state The authors have learned to follow the elimination of H[sub 2] and C[sub 2]H[sub 6] from bimolecular Ni[sup +](n-butane) complexes in real time, on a 50-ns time scale In M[sup +] reactions, the authors can control the kinetic energy and the electronic state of the reactants A key advantage in interpreting these results is that one understands the electronic structure of the bare metal atom reactants very well Solution-phase chemists might well question the relevance of atomic species with genuine 1+ or 2+ charges and no ligands or solvent to the [open quotes]real world[close quotes] of organometallic chemistry Yet connections surely exist, as witnessedmore » by the fact that Rh and Ir atoms are unusually reactive in all phases Theoretical chemists are beginning to provide a conceptual framework that will unify seemingly diverse branches of experimental chemistry Of necessity, the ab initio quantum chemist works on model transition metal systems, draws experimental evidence from all available sources, and tries to abstract from the calculations what is robust and common to all phases Gas-phase metal atoms are idealized model systems well matched to the capabilities of modern theory Many new conceptual insights in the next 10 years will come from careful analysis of ab initio wave functions informed by incisive gas-phase experiments 30 refs, 5 figs, 1 tab« less
281 citations
TL;DR: In this paper, the C-H bond of a terminal methyl group of an alkyl chain can be oxidatively added to the anchored transition-metal ion M{sup +} (Scheme II).
Abstract: Gas-phase experiments with naked transition-metal ions offer a unique opportunity to probe, in the absence of any solvation, ion-pairing, and/or ligand effects, the intrinsic properties of reactive organometallic species and to evaluate the potential role these remarkable transients play in the initial steps of the activation of C-H and C-C bonds. Not surprisingly, this topic is of fundamental interest in catalysis and has attracted considerable attention in the last decade. The authors and later others, have recently demonstrated that remote functionalization can be achieved in the gas phase for quite a variety of flexible substrates including aliphatic nitriles, isonitriles, amines, alcohols, ketones, alkynes, and allenes, respectively. Specifically, we have shown that the C-H bond of a terminal methyl group of an alkyl chain can be oxidatively added to the anchored transition-metal ion M{sup +} (Scheme II). The insertion is followed by a {beta}-hydrogen shift (5 {yields} 6) or {beta}-cleavage of the C-C bond (5 {yields} 7) to generate intermediates from which eventually reductive elimination of H{sub 2} of ligand detachment occurs. This discussion will be confined to recent results from our laboratory. While most of the data will be concerned with the chemistry of aliphatic nitriles, the reactions of alkynesmore » with bare transition-metal ions will be briefly mentioned.« less
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124 citations
June1
TL;DR: In this article, the authors focus on the Reaktivitat einiger MO+-Ionen nicht immer mit einer geringen Regioselektivat verbunden; so bewirken FeO+Ionen in der Gasphase die regio-spezifische Aktivierung von γ-C-H-Bindungen in Dialkylketonen.
Abstract: Innerhalb des letzten Jahrzehnts erfuhr die Gasphasenchemie isolierter Ubergangsmetalloxid-Kationen MO+ betrachtliche Aufmerksamkeit. Dieses Interesse beruht in erster Linie auf der besonderen Rolle von Metalloxid-Spezies bei der Oxidation organischer Verbindungen in einer Vielzahl chemischer und biochemischer Umwandlungen. Auf molekularer Ebene dienen als einfachstes Modellsystem fur derartige Prozesse die Reaktionen „nackter” Metalloxid-Ionen in der Gasphase. Aufgrund der hohen Oxophilie „fruher” Ubergangsmetalle vermitteln ihre Monoxid-Kationen keinen Sauerstoffatom-Transfer auf organische Verbindungen. Im Gegensatz dazu sind Monoxid-Kationen „spater” Ubergangsmetalle sehr wohl zur Oxygenierung vieler Kohlenwasserstoffe geeignet, und die reaktivsten Ionen, MnO+, FeO+, NiO+, OsO+ und PtO+, aktivieren selbst Methan. Durch die Analyse von Reaktionskinetik, Isotopeneffekten, Produktverteilungen etc. kann man Einblick in die Reaktionsmechanismen dieser Oxidationsprozesse gewinnen. Dabei erweist sich oftmals die Aktivierug von C–H-Bindungen fur die Reaktionen von MO+ mit Alkanen als geschwindigkeitsbestimmend. Interessanterweise ist die hohe Reaktivitat einiger MO+-Ionen nicht immer mit einer geringen Regioselektivitat verbunden; so bewirken FeO+-Ionen in der Gasphase die regio-spezifische Aktivierung von γ-C–H-Bindungen in Dialkylketonen. Im Vergleich zur Reaktion in kondensierter Phase erweist sich die Epoxidierung von Olefinen in der Gasphase als unerwartet komplex. Dies ist im wesentlichen dadurch bedingt, das das den Sauerstoff transferierende Metall-Ion eine Isomerisierung der intermediar entstehenden Epoxide zu den stabileren Aldehyden oder Ketonen katalysiert. Aromatische Verbindungen konnen ebenfalls durch MO+-Ionen hydroxyliert werden; insbesondere die Gasphasenoxidation von Benzol durch „nacktes” FeO+ zeigt bemerkenswerte Parallelen zur Metabolisierung von Arenen. Daruber hinaus ermoglicht die Ionen-Cyclotron-Resonanz-Massenspektrometrie eine katalytische Reaktionsfuhrung, bei der ein einzelnes Metall-Ion in einer Folge von ausschlieslich bimolekularen Reaktionen mehr als ein Substratmolekul in ein oxygeniertes Produkt umwandelt. Die bemerkenswertesten Beispiele sind bisher die Pt+-vermittelte Oxidation von Methan durch molekularen Sauerstoff und die durch Co+-Ionen vermittelte Hydroxylierung von Benzol durch N2O als Oxidans. Schlieslich werden die wesentlichen Eigenschaften von Gasphasenreaktionen mit Beobachtungen in kondensierter Phase korreliert, bei denen vermutet wird, das Metalloxid-Spezies eine Schlusselrolle spielen. Das Ergebnis dieses Vergleichs ist insofern vielversprechend, als das Verstandnis von ubergangsmetallkatalysierten Oxidationen in der Gasphase zu einer einheitlichen Beschreibung dieser Prozesse auf molekularer Ebene fuhren kann. Es bleibt zu hoffen, das Gasphasenuntersuchungen einen wichtigen Beitrag fur die Entwicklung von masgeschneiderten Katalysatoren liefern werden.
123 citations
TL;DR: In this article, the gas-phase reactivities of metal dioxide cations MO2+ towards simple hydrocarbons were characterized using Fourier transform mass spectrometers. But the results were limited to the case of vanadyl cation VO2+ and NbO2+ in which no radical losses occurred.
121 citations
References
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TL;DR: The Fourier transform ion cyclotron resonance (FT-ICR) 1.5 mass spectrometer as discussed by the authors was developed for mass spectroscopy and it can be used to obtain the whole spectrum in a very short period of time.
957 citations
387 citations
TL;DR: In this paper, the authors demonstrated that frequency-sweep excitation can provide the broad-band irradiation required to excite ion cyclotron resonances throughout any desired mass range.
355 citations
315 citations
TL;DR: Fourier transform infrared (FT-IR) interferometry and nuclear magnetic resonance (NMR) spectroscopy is the most versatile technique for unscrambling and quantifying ion-molecule reaction kinetics and equilibria in the absence of solvent as discussed by the authors.
Abstract: As for Fourier transform infrared (FT-IR) interferometry and nuclear magnetic resonance (NMR) spectroscopy, the introduction of pulsed Fourier transform techniques revolutionized ion cyclotron resonance mass spectrometry: increased speed (factor of 10,000), increased sensitivity (factor of 100), increased mass resolution (factor of 10,000—an improvement not shared by the introduction of FT techniques to IR or NMR spectroscopy), increased mass range (factor of 500), and automated operation. FT-ICR mass spectrometry is the most versatile technique for unscrambling and quantifying ion-molecule reaction kinetics and equilibria in the absence of solvent (i.e., the gas phase). In addition, FT-ICR MS has the following analytically important features: speed (∼1 second per spectrum); ultrahigh mass resolution and ultrahigh mass accuracy for analysis of mixtures and polymers; attomole sensitivity; MS n with one spectrometer, including two-dimensional FT/FT-ICR/MS; positive and/or negative ions; multiple ion sources (especially MALDI and electrospray); biomolecular molecular weight and sequencing; LC/MS; and single-molecule detection up to 10 8 Dalton. Here, some basic features and recent developments of FT-ICR mass spectrometry are reviewed, with applications ranging from crude oil to molecular biology.
305 citations