Gold Trifluoromethyl Complexes as Efficient Regioselective Catalysts in Alkyne Hydration.

Gold(III) complexes containing trifluoromethyl ligands are efficient catalysts in the hydration of alkynes, operating at low catalyst loadings, without additives, using environmentally friendly solvents and at mild conditions (60 °C). Hydration of terminal and internal alkynes provides the corresponding ketones in quantitative yields without special precautions as dry solvents or inert atmospheres. Remarkably, hydration of asymmetric internal alkynes proceeds with moderate to notable regioselectivities, providing mixtures of the two possible isomers with ratios up to 90 : 10.

The CF Group as a Synthon of the CF Unit in Palladium Chemistry.

The homoleptic trifluoromethyl-palladium(II) complex [Pd(CF)] (1) is shown to be highly active towards amines. Thus, when treated with primary amines RNH, it readily undergoes aminolysis of one of the CF ligands affording the isocyanide complexes [(CF)Pd(CNR)] (R=aryl). In this process the original CF group undergoes total defluorination.

Synthesis and Lewis Acid Properties of Neutral Silver(III) Adducts Containing the Ag(CF) Moiety.

The acetonitrile Ag complex [Ag(CF)(NCCH)] (2) has been reported independently by Eujen and Naumann in the last century, albeit with intriguing NMR discrepancy. In their reports, 2 was claimed to be obtained starting from either [Ag(CF)Cl] (3⋅) or [Ag(CF)] (1) via halide abstraction using AgNO or acidic treatment, resp. These two synthetic routes are herein reinvestigated.

The Fluoride Method: Access to Silver(III) NHC Complexes.

We have synthesized the first silver(III) carbene complexes, (CF ) Ag(NHC), by direct reaction of the silver(III) fluoride precursor complex [PPh ][(CF ) AgF] with different imidazolium salts. This novel methodology circumvents the use of free NHC molecules. The silver(III) carbene complexes thus prepared are unprecedented and show remarkable thermal stabilities.

Electrophilicity of neutral square-planar organosilver(III) compounds.

Neutral Ag(III) complexes stabilised with just monodentate ligands are here unambiguously established. In a series of square-planar (CF)Ag(L) compounds with hard and soft Group 15 donor ligands, L, the metal center has been found to exhibit substantial acidity favouring apical coordination of an additional ligand under no coordination constraints.

Terminal Au-N and Au-O Units in Organometallic Frames.

Since gold is located well beyond the oxo wall, chemical species with terminal Au-N and Au-O units are extremely rare and limited to low coordination numbers. We report here that these unusual units can be trapped within a suitable organometallic frame. Thus, the terminal auronitrene and auroxyl derivatives [(CF ) AuN] and [(CF ) AuO] were identified as local minima by calculation.

Heteropolymetallic Architectures as Snapshots of Transmetallation Processes at Different Degrees of Transfer.

Novel heteropolymetallic architectures have been built by integrating Pd, Au and Ag systems. The dinuclear [(CNC)(PPh )Pd- M(PPh )](ClO ) ( M=Au (3), Ag (4); CNC=2,6-diphenylpyridinate) and trinuclear [{(CNC)(PPh )Pd} M](ClO ) ( M=Au (6), Ag (5)) complexes have been accessed or isolated. Structural and DFT characterization unveil striking interactions of one of the aryl groups of the CNC ligand(s) with the M center, suggesting these complexes constitute models of transmetallation processes.

Stability of Ag towards Halides in Organosilver(III) Complexes.

The involvement of silver in two-electron Ag /Ag processes is currently emerging. However, the range of stability of the required and uncommon Ag species is virtually unknown. Here, the stability of Ag towards the whole set of halide ligands in the organosilver(III) complex frame [(CF ) AgX] (X=F, Cl, Br, I, At) is theoretically analyzed.

Hydrogen bonding to metals as a probe for an inverted ligand field.

Electron-rich, late transition metals are known to act as hydrogen-bonding (HBd) acceptors. In this regard, Pt(ii) centres in square-planar environments are particularly efficient. It is however puzzling that no convincing experimental evidence is currently available for the isoelectronic neighbour Au(iii) being involved in HBd interactions.

Metal-Metal Cooperation in the Oxidation of a Flapping Platinum Butterfly by Haloforms: Experimental and Theoretical Evidence.

The model -DFT for the butterfly complex [{Pt(CC*)(μ-pz)}] (; HCC* = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1-imidazol-2-ylidene) shows two minima in the potential energy surface of the ground state in acetone solution: the butterfly-wing-spreading molecules , ( ≈ 3.20 Å) and the wing-folding molecules ( ≤ 3.00 Å).

The First Organosilver(III) Fluoride, [PPh ][(CF ) AgF].

Organosilver(III) fluoride complexes have been assigned a key role in different fluorination processes. To the best of our knowledge, however, none of them seem to have been isolated or even detected thus far. Here we report on the successful synthesis of the trifluoromethyl derivative [PPh ][(CF ) AgF], which has been isolated in high yield.

M-C Bond Homolysis in Coinage-Metal [M(CF ) ] Derivatives.

A comparative study of the homoleptic [M(CF ) ] complexes of all three coinage metals (M=Cu, Ag, Au) reveals that homolytic M-C bond cleavage is favoured in every case upon excitation in the gas phase (CID-MS ). Homolysis also occurs in solution by photochemical excitation. Transfer of the photogenerated CF radicals to both aryl and alkyl carbon atoms was also confirmed.

Platinum-mediated monohydration of SO.

The monohydration of SO2 has been achieved in solution mediated by a platinum-aquo complex. Benzamidate ligands play a key role along the process, acting as versatile proton shuttles. Finally, the platinum center allows the stabilization of benzimidic acid and a hydrogensulphite anion, the disfavored tautomers of benzamide and sulphonate, respectively.

A Cyclometalated N-Heterocyclic Carbene: The Wings of the First Pt (II,II) Butterfly Oxidized by CHI.

The X-ray study on a single crystal of the butterfly-like complex [{Pt(C^C*)(μ-pz)} ] (1), containing a cyclometalated N-heterocyclic carbene ligand as wings (HC^C*=1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene), showed three molecules in the asymmetric unit with intermetallic separations (Å) of 3.2294(4) (1A), 3.2834(4) (1B), and 3.

Homoleptic Trifluoromethyl Derivatives of Ag and Ag.

The homoleptic silver(I) compound [PPh ][CF AgCF ] (1) provides a convenient entry to the homoleptic silver(III) derivative [PPh ][Ag(CF ) ] (2). Once isolated as pure substances, these compounds exhibit marked thermal stabilities. Their structural and spectroscopic properties have been experimentally established.

Pt-M Complexes (M=Ag, Au) as Models for Intermediates in Transmetalation Processes.

Heteropolynuclear complexes [(CNC)(PPh )PtM(PPh )]ClO [M=Au (1), Ag (2)] and [{Pt(CNC)(PPh )} M]ClO [M=Ag (3), Au (4); CNC=2,6-diphenylpyridinate] were prepared and studied by X-ray crystallography, spectroscopic techniques, and DFT calculations. The X-ray crystal structures of 1, 3, and 4 confirmed the existence of Pt-M bonds and M⋅⋅⋅C interactions involving one of the phenyl fragments of CNC. Their NMR spectra showed the persistence of the Pt-M interactions in solution and also revealed an intramolecular metronome-like dynamic process consisting of back-and-forth motion of the acidic M fragments along the C-Pt-C axis.

An Organogold(III) Difluoride with a trans Arrangement.

The trans isomer of the organogold(III) difluoride complex [PPh ][(CF ) AuF ] has been obtained in a stereoselective way and in excellent yield by reaction of [PPh ][CF AuCF ] with XeF under mild conditions. The compound is both thermally stable and reactive. Thus, the fluoride ligands are stereospecifically replaced by any heavier halide or by cyanide, the cyanide affording [PPh ][trans-(CF ) Au(CN) ].

Gold(II) Trihalide Complexes from Organogold(III) Precursors.

The mononuclear gold(II) halide complexes [AuCl ] and [AuBr ] are formed in the gas phase by collision-induced homolytic splitting of the only Au-C bond in the monoalkylgold(III) precursors [CF AuX ] . The geometries of the whole series of [AuX ] complexes (X=F, Cl, Br, I) have been calculated by DFT methods. It has also been found that the neutral AuX molecules behave as unsaturated species, showing significant affinity for an additional X ligand.

(CF ) Au as a Highly Acidic Organogold(III) Fragment.

The Lewis acidity of perfluorinated trimethylgold (CF ) Au was assessed by theoretical and experimental methods. It was found that the (CF ) Au unit is much more acidic than its nonfluorinated analogue (CH ) Au, and probably sets the upper limit of the acidity scale for neutral organogold(III) species R Au. The significant acidity increase on fluorination is in line with the CF group being more electron-withdrawing than CH .

Catalytic Dehydrogenative Coupling of Hydrosilanes with Alcohols for the Production of Hydrogen On-demand: Application of a Silane/Alcohol Pair as a Liquid Organic Hydrogen Carrier.

The compound [Ru(p-cym)(Cl) (NHC)] is an effective catalyst for the room-temperature coupling of silanes and alcohols with the concomitant formation of molecular hydrogen. High catalyst activity is observed for a variety of substrates affording quantitative yields in minutes at room temperature and with a catalyst loading as low as 0.1 mol %.

Anionic Derivatives of Perfluorinated Trimethylgold.

The homoleptic compound [PPh ][CF AuCF ] cleanly undergoes photoinduced oxidative addition of CF I to afford the organogold(III) derivative [PPh ][(CF ) AuI] in good yield and under mild conditions. This compound provides a convenient entry to the chemistry of the perfluorinated (CF ) Au fragment, the properties of which were analyzed with the aid of DFT methods and compared with those of the homologous non-fluorinated (CH ) Au moiety. It was found that reductive elimination of CX -CX in the former (X=F) requires a much higher energy barrier than in the latter (X=H) and is therefore considerably less favored.

Gold(I) Fluorohalides: Theory and Experiment.

The anionic trifluoromethylgold(I) derivatives [CF AuX] , which have been prepared and isolated as their [PPh ] salts in good yield, undergo thermally induced difluorocarbene extrusion in the gas phase, giving rise to the mixed gold(I) fluorohalide complexes [F-Au-X] (X=Cl, Br, I). These triatomic species have been detected by tandem mass spectrometry (MS2) experiments and their properties have been analyzed by DFT methods. The CF extrusion mechanism from the Au-CF moiety serves as a model for the CF insertion into the Au-F bond, since both reactivity channels are connected by the microreversibility principle.

Unusual Metal-Metal Bonding in a Dinuclear Pt-Au Complex: Snapshot of a Transmetalation Process.

The dinuclear Pt-Au complex [(CNC)(PPh3 )Pt Au(PPh3 )](ClO4 ) (2) (CNC=2,6-diphenylpyridinate) was prepared. Its crystal structure shows a rare metal-metal bonding situation, with very short Pt-Au and Au-Cipso (CNC) distances and dissimilar Pt-Cipso (CNC) bonds. Multinuclear NMR spectra of 2 show the persistence of the Pt-Au bond in solution and the occurrence of unusual fluxional behavior involving the [Pt(II) ] and [Au(I) ] metal fragments.