Synthesis and reactivity of [Au(NHC)(Bpin)] complexes.

A new class of [Au(NHC)(Bpin)] complexes has been synthesized and their unusual reactivity was investigated using computational and experimental methods. The gold-boryl complexes exhibit unexpected high stability and reactivity.

A simple synthetic entryway into palladium cross-coupling catalysis.

The simple synthesis of a family of palladates containing an imidazolium counterion is presented. These "ate" complexes can be easily converted into well-defined palladium-N-heterocyclic carbene (NHC) complexes. The synthetic protocols leading to the "ate" and to the Pd-NHC neutral complexes have been exemplified with various NHC ligands. The palladates prove efficient pre-catalysts enabling Suzuki-Miyaura and Mizoroki-Heck reactions.

Hydrofluorination of Alkynes Catalysed by Gold Bifluorides.

We report the synthesis of nine new N-heterocyclic carbene gold bifluoride complexes starting from the corresponding N-heterocyclic carbene gold hydroxides. A new methodology to access N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) fluoride starting from N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) hydroxide and readily available potassium bifluoride is also reported. These gold bifluorides were shown to be efficient catalysts in the hydrofluorination of symmetrical and unsymmetrical alkynes, thus affording fluorinated stilbene analogues and fluorovinyl thioethers in good to excellent yields with high stereo- and regioselectivity. The method is exploited further to access a fluorinated combretastatin analogue selectively in two steps starting from commercially available reagents.

A short and modular synthesis of bulky and electron-rich N-phosphinomethyl-functionalised N-heterocyclic carbene complexes.

Bulky and electron-rich N-phosphinomethyl-substituted N-heterocyclic carbene transition metal complexes have been prepared in a short and efficient protocol. The modular synthesis allows one to convert borane-protected phosphino-functionalized imidazolium salts into their corresponding metal chelate complexes in a one-pot procedure.

Imidazole to NHC rearrangements at molybdenum centers: an experimental and theoretical study.

Both manganese and rhenium complexes of the type [M(bipy)(CO)(3)(N-RIm)](+) (bipy=2,2'-bipyridine) undergo deprotonation of the central CH group of the N-alkylimidazole (N-RIm) ligand when treated with a strong base. However, the outcome of the reaction is very different for either metal. For Mn, the addition of the equimolar amount of an acid to the product of the deprotonation affords an N-heterocyclic carbene (NHC) complex, whereas for Re, once the deprotonation of the central imidazole CH group has occurred, the bipy ligand undergoes a nucleophilic attack on an ortho carbon, affording the C-C coupling product. The extension of these studies to pseudo-octahedral [Mo(η(3)-allyl)(bipy)(CO)(2)(N-RIm)](+) complexes has allowed us to isolate cationic NHC complexes (Mn(I)-type behavior), as well as their neutral imidazol-2-yl precursors. Theoretical studies of the reaction mechanisms using DFT computations were carried out on the deprotonation of [Mn(bipy)(CO)(3)(N-PhIm)](+), [Re(bipy)(CO)(3) (N-MesIm)](+), and [Mo(η(3)-C(4)H(7))(bipy)(CO)(2) (N-MesIm)](+) complexes (Mes=mesityl) at the B3LYP/6-31G(d) (LANL2DZ for Mn, Re, and Mo) level of theory. Our results explain why different products have been found experimentally for Mn, Mo, and Re complexes. For Re, the process leading to a C-C coupling product is clearly more favored than those forming an imidazol-2-yl product. In contrast, for Mn and Mo complexes, the lower stabilizing interaction between the central imidazole and ortho bipy C atoms, along with the higher lability of the ligands, make the formation of an NHC-type product kinetically more accessible, in good agreement with experimental findings.