Ruthenium Janus-Head Complexes with a Triazolediylidene Ligand. Structural Features and Catalytic Applications

The use of the ligand triazolediylidene (ditz), has afforded the preparation of two new complexes of Ru in which the ligand is bridging two metal fragments in a facially opposed (Janus-head) disposition. One of the complexes is dinuclear (2) and the other tetranuclear (3). The tetranuclear compound displays interesting structural features, as shown by the X-ray diffraction studies. The two complexes have been tested in the catalytic β-alkylation of secondary alcohols with primary alcohols, providing high activities when both aliphatic and aromatic alcohols are used.

An N-heterocyclic carbene/iridium hydride complex from the oxidative addition of a ferrocenyl-bisimidazolium salt: implications for synthesis.

Synthesis and Reactivity of New Complexes of Rhodium and Iridium with Bis(dichloroimidazolylidene) Ligands. Electronic and Catalytic Implications of the Introduction of the Chloro Substituents in the NHC Rings

The preparation of a new bis(dichloroimidazolylidene) ligand has provided chelate-N-heterocyclic complexes of Rh(I) and Ir(I), which have been fully characterized. The crystal structures of three of the new complexes are described. The study of the electronic properties of the new ligands was made on the basis of the ν(CO) stretching frequencies of the carbonyl derivatives, showing that the chloroimidazolylidene ligand is significantly less σ-donating than the related nonchlorinated analogue. This electronic modification of the ligand has important implications for the catalytic properties of the compounds obtained, as observed from enhanced activity shown in catalytic hydrosilylation of te…

Preparation of a Series of “Ru(p-cymene)” Complexes with Different N-Heterocyclic Carbene Ligands for the Catalytic β-Alkylation of Secondary Alcohols and Dimerization of Phenylacetylene

A series of five different “(p-cymene)Ru(NHC)” complexes (NHC = imidazolin-2-ylidene, imidazolin-4-ylidene, and pyrazolin-3-ylidene) have been obtained and fully characterized. The crystal structure of two of the new complexes has been determined by X-ray diffraction methods. All five complexes have been tested in the catalytic β-alkylation of secondary alcohols with primary alcohols and the dimerization of phenylacetylene, showing an excellent activity in both processes. A clear improvement on the catalytic activity of the complexes is observed when the more basic NHC ligands are used. The pyrazolylidene-Ru complex lies among the best catalysts for the β-alkylation of secondary alcohols re…

Electrospray Ionization Mass Spectrometry Studies on the Mechanism of Hydrosilylation of Terminal Alkynes Using an N-Heterocyclic Carbene Complex of Iridium, Allow Detection/Characterization of All Reaction Intermediates

A new pyridine-4,5-dichloroimidazol-2-ylidene complex of Ir(I) has been obtained, and its catalytic activity toward hydrosilylation of phenylacetylene and 4-aminophenylacetylene has been studied. T...