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The PCP pincer complex, IrH 2 {C 6 H 3 -2,6-(CH 2 P-t-Bu 2 ) 2 } (1) catalyzes the transfer dehydrogenation of primary and secondary alcohols. Dehydrogenation occurs across the C-O bond rather than the C-C bonds and the corresponding aldehydes or ketones are obtained as the sole products arising from the dehydrogenation reactions. Methanol is an exception to this pattern of reactivity and undergoes only stoichiometric dehydrogenation with 1 to give the carbonyl complex, Ir(CO){C 6 H 3 -2,6-(CH 2 P-t-Bu 2 ) 2 } (2). The products are obtained in nearly quantitative yields when the reactions are carried out in toluene solutions. Under the same conditions, 2,5-hexanediol is converted to the annulated product, 3-methyl-2-cyclopenten-1-one which has been isolated in 91% yield in a preparative scale reaction.Résumé : Le complexe PCP en forme de pince, IrH 2 {C 6 H 3 -2,6-(CH 2 P-t-Bu 2 ) 2 } (1) catalyse la réaction de déshydrogé-nation par transfert des alcools primaires et secondaires. La déshydrogénation se fait à travers la liaison C-O plutôt qu'à travers les liaisons C-C et on n'obtient que les aldéhydes et les cétones comme seuls produits de ces réactions de déshydrogénation. Le méthanol est une exception à ce mode de réactivité et il ne subit qu'une déshydrogénation stoechiométrique avec 1 pour conduire à la formation d'un complexe de carbonyle, Ir(CO){C 6 H 3 -2,6-(CH 2 P-t-Bu 2 ) 2 } (2). Lorsqu'on effectue les réactions en solution dans le toluène, les produits sont obtenus en rendements pratiquement quantitatifs. Dans les mêmes conditions, l'hexane-2,5-diol est transformé en produit cyclique, la 3-méthylcyclopent-2-én-1-one qui a été isolée avec un rendement de 91% au cours d'une réaction à l'échelle préparative.

A simple synthesis method of silver nanoparticles and its application as an active surface-enhanced Raman spectroscopy (SERS) colloid are presented in this work. The photoreduction of AgNO 3 in presence of sodium citrate (NaCit) was carried out by irradiation with different light sources (UV, white, blue, cyan, green, and orange) at room temperature. The evaluation of silver nanoparticles obtained as a function of irradiation time (1-24 h) and light source was followed by UV-visible absorption spectroscopy. This light-modification process results in a colloid with distinctive optical properties that can be related to the size and shape of the particles. The Ag colloids, as prepared, were employed as active colloids in SERS. Pyridine and caffeine were used as test molecules.

The behavior of palladium C-bound enolates [Pd(CH2C(O)CR3)Cl(PPh3)2] (R = H, 1; R = Me, 2) and [Pd(CH2C(O)CR3)(PPh3)2(NCMe)](BF4) (R = H, 5; R = Me, 6) has been studied. Dimeric species with bridging enolate moieties are formed in solution when a coordination site on the metal is made available, either with Pd2{μ-κ2-C,O-CH2C(O)CR3}2 or with mixed Pd2{μ-κ2-C,O-CH2C(O)CR3}(μ-X) (X = Cl, OH) bridges. It is proposed that π back-donation is important to stabilize oxygen bonding. Complexes 1 and 2 undergo exchange between free and coordinated phosphine in solution. Kinetic experiments support an intramolecular associative mechanism which could involve an oxoallyl-like transition state. The reactivity of the complexes has been explored. Some reactions typical of Pd-alkyls have been observed such as insertion of CO to give CR3C(O)CH2COOH. Electrophilic attack on oxygen is very important:  the hydrolysis of the enolate complexes has been studied and also the reaction with ClSiMe3 to give silyl enol ethers.