5.1. Nanoalloys of Group 11 (Cu, Ag, Au) 865 5.1.1. Cu−Ag 866 5.1.2. Cu−Au 867 5.1.3. Ag−Au 870 5.1.4. Cu−Ag−Au 872 5.2. Nanoalloys of Group 10 (Ni, Pd, Pt) 872 5.2.1. Ni−Pd 872 * To whom correspondence should be addressed. Phone: +39010 3536214. Fax:+39010 311066. E-mail: ferrando@fisica.unige.it. † Universita di Genova. ‡ Argonne National Laboratory. § University of Birmingham. | As of October 1, 2007, Chemical Sciences and Engineering Division. Volume 108, Number 3

Nanoalloys: From Theory to Applications of Alloy Clusters and Nanoparticles

Pore size determination in modified micro- and mesoporous materials. Pitfalls and limitations in gas adsorption data analysis

Sterically encumbered Lewis acid and Lewis base combinations do not undergo the ubiquitous neutralization reaction to form "classical" Lewis acid/Lewis base adducts. Rather, both the unquenched Lewis acidity and basicity of such sterically "frustrated Lewis pairs (FLPs)" is available to carry out unusual reactions. Typical examples of frustrated Lewis pairs are inter- or intramolecular combinations of bulky phosphines or amines with strongly electrophilic RB(C(6)F(5))(2) components. Many examples of such frustrated Lewis pairs are able to cleave dihydrogen heterolytically. The resulting H(+)/H(-) pairs (stabilized for example, in the form of the respective phosphonium cation/hydridoborate anion salts) serve as active metal-free catalysts for the hydrogenation of, for example, bulky imines, enamines, or enol ethers. Frustrated Lewis pairs also react with alkenes, aldehydes, and a variety of other small molecules, including carbon dioxide, in cooperative three-component reactions, offering new strategies for synthetic chemistry.

Frustrated Lewis pairs: metal-free hydrogen activation and more.

Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases in solution that are deterred from strong adduct formation by steric and/or electronic factors. This opens pathways to novel cooperative reactions with added substrates. Small-molecule binding and activation by FLPs has led to the discovery of a variety of new reactions through unprecedented pathways. Hydrogen activation and subsequent manipulation in metal-free catalytic hydrogenations is a frequently observed feature of many FLPs. The current state of this young but rapidly expanding field is outlined in this Review and the future directions for its broadening sphere of impact are considered.

Frustrated Lewis pair chemistry: development and perspectives.

http://alpha.chem.umb.edu/chemistry/ch611/documents/C-Htransitionmetalbonds.pdf

Carbonhydrogen-transition metal bonds

Great advances have been made in the past decade in the field of NMR spectroscopy. Apart from the development of completely new areas of application, such as in solid-state chemistry, in materials science, in physiological chemistry, and in medicine, with the introduction of new pulse spectroscopic methods and the application of high magnetic field strengths important progress has also been made in the traditional field of high-resolution NMR spectroscopy. Thus, among other things, the observation of metal resonances has been facilitated and new areas of application have been opened up in inorganic and organometallic chemistry. In this review, recent detection methods for spin-1/2 and quadrupolar metal nuclei are presented and discussed. The use of metal-NMR spectroscopy with respect to problems of a typical chemical nature, mainly from the field of organometallics, is demonstrated for a number of selected metal nuclei (25Mg, 27Al, 49Ti, 57Fe, 59Co, 61Ni, 91Zr, 103Rh, and 195Pt). Relations found empirically between chemical shifts and coordination number, oxidation number, and electronic configuration of a metal bound in a complex are emphasized. Furthermore, cases in which the chemical shifts of metal nuclei can be interpreted in terms of the energy difference of frontier orbitals are presented. This aspect leads to the establishment of a relationship between chemical reactivity and NMR parameters for a series of related compounds.

High‐Resolution Metal NMR Spectroscopy of Organometallic Compounds [New Analytical Methods (30)]

27AI‐NMR Spectroscopy: A Probe for Three‐, Four‐, Five‐, and Sixfold Coordinated Al Atoms in Organoaluminum Compounds

Die Reaktion des Zirconocendichlorids mit zwei Aquivalenten n-Butyllithium und Trimethylphosphan liefert (1-Buten)(trimethylphosphan)zirconocen (1) in 83 proz. Ausbeute. Komplex 1 ist ein ausgezeichnetes Ausgansmaterial zur Darstellung weiterer (Alken)- oder (Alkin)zirconocen-Komplexe; so erhalt man durch Verdrangung des 1-Butens mit Ethylen, Styrol oder Tolan die Zirconocen-Komplexe 2, 3 oder 7 in hohen Ausbeuten. Eine weitere Darstellungsmethode fur (1-Alken)(trimethylphosphan)zirconocen-Komplexe ist die Umsetzung von Zirconocendichlorid mit 1-Alkylmagnesiumhalogeniden in Gegenwart von Trimethylphosphan bei Raumtemperatur; z. B. sind so der 1-Propen-Komplex 9 und der 1-Penten-Komplex 10 gut zuganglich. Spektroskopische Untersuchungen (1H-, 13C- und 31P-NMR) zeigen, das alle dargestellten (1-Alken)(trimethylphosphan)zirconocen-Komplexe in Losung bei 0°C als getrennt beobachtbare Rotamerenpaare 1a, b, 3a, b, 9a, b und 10a, b im Verhaltnis ca. 4:1 vorliegen. Die Strukturen des Ethylen-Komplexes 2 und des Styrol-Komplexes 3a wurden zusatzlich durch Kristallstrukturanalysen ermittelt.



1-Alkene)trimethylphosphine)zirconocenes: Preparation, Characterization, and Reactivity



(1-Butene)(trimethylphosphine)zirconocene (1) is prepared in 83% yield by subsequent reaction of zirconocene dichloride with two equivalents of n-butyllithium and trimethylphosphine. Reaction of complex 1 with other alkenes or alkynes, e.g. ethylene, styrene, or tolane indicates that this compound is an ideal starting material for synthezising other (alkene)- or (alkyne)zirconocene complexes, e.g. 2, 3, or 7. Another route to (1-alkene)(trimethylphosphine)zirconocenes, e.g. the 1-propene complex 9 or the 1-pentene complex 10, is the reaction of zirconocene dichloride with 1-alkylmagnesium halide in the presence of trimethylphosphine at room temperature. Spectroscopic investigations 1H-, 13C-, and 31P-NMR spectroscopy) confirm that in solution, complex 1 as well as the other 1-alkene complexes 3, 9, and 10 exist as a mixture of two rotamers 1a, b, 3a, b, 9a, b, and 10a, b in a ca. 4:1 ratio. The structures of the ethylene complex 2 and the styrene complex 3a are also determined by X-ray analyses.

(1‐Alken)(trimethylphosphan)zirconocen‐Komplexe: Darstellung, Charakterisierung und Reaktivität

27Al-NMR-Spektroskopie zur Charakterisierung von Organoaluminium-Verbindungen

Der NMR-Spektroskopie wurden in den vergangenen Jahren vollig neue Anwendungsfelder erschlossen, z. B. bei der Untersuchung von Festkorpern, in der Materialforschung, in der Physiologischen Chemie und in der Medizin; aber auch auf ihren traditionellen Gebieten wurden dank neuer Pulsmethoden und starkerer Magnetfelder bedeutende Fortschritte erzielt. So wurde unter anderem die Beobachtung der Resonanzsignale von Metallkernen entscheidend erleichtert. In diesem Aufsatz werden neuere Methoden der NMR-Spektroskopie zur Untersuchung sowohl von Metallkernen mit einer Kernspinquantenzahl 1/2 als auch von solchen mit einem Kernquadrupolmoment vorgestellt; vor allem an Organometallverbindungen wird die Aussagekraft der chemischen Verschiebung ausgewahlter Metallkerne (25Mg, 27Al, 49Ti, 57Fe, 59Co, 61Ni, 91Zr, 103Rh und 195Pt) demonstriert. Hierbei stehen empirisch gefundene Zusammenhange zwischen chemischer Verschiebung und Koordinationszahl, Oxidationsstufe sowie Elektronenkonfiguration eines komplexgebundenen Metallatoms im Vordergrund. Daruber hinaus wird an einigen Beispielen die chemische Verschiebung des Metallkerns anhand einer Betrachtung der Grenzorbitale der Komplexe interpretiert und damit zur Reaktivitat der Komplexe in Beziehung gesetzt.

Anna Rufińska

Papers

High‐Resolution Metal NMR Spectroscopy of Organometallic Compounds [New Analytical Methods (30)]

27AI‐NMR Spectroscopy: A Probe for Three‐, Four‐, Five‐, and Sixfold Coordinated Al Atoms in Organoaluminum Compounds

(1‐Alken)(trimethylphosphan)zirconocen‐Komplexe: Darstellung, Charakterisierung und Reaktivität

27Al-NMR-Spektroskopie zur Charakterisierung von Organoaluminium-Verbindungen

Hochauflösende Metallkern-NMR-Spektroskopie von Organometallverbindungen