New, potentially chelating NHC ligands; synthesis, complexation studies, and preliminary catalytic evaluation.

Two new N-heterocyclic carbene (NHC) ligands bearing 2-morpholino and 2-piperidinyl naphthyl wingtips were synthesised (2-SIMorNap and 2-SIPipNap). Nuclear magnetic resonance studies, in conjunction with crystal structures and derivatisation of the NHC salts using a chiral counteranion, revealed that the ligand wingtips are oriented anti with respect to each other. From the free carbene, palladium, ruthenium and iridium complexes were prepared. NHC-iridium dicarbonyl complexes were made in order to extract the TEP values for these ligands. The study showed that these NHC ligands are more electron-donating than normal, aryl-substituted NHCs. The palladium complexes were tested in representative Suzuki-Miyaura cross-coupling reactions and compared to the state of the art systems. Ruthenium-catalysed ring-closing metathesis with these ligands was also performed. It was found that Grubbs' 2nd generation catalyst incorporating 2-SIPipNap did not initiate at room temperature and required heating for RCM to occur.

Flexible C2-symmetric bis-sulfoxides as ligands in enantioselective 1,4-addition of boronic acids to electron-deficient alkenes.

The application of acyclic C2-symmetric chelating bis-sulfoxide ligands in the Rh(I)-catalyzed enantioselective 1,4-addition of boronic acids to electron-deficient alkenes is reported. Among the acyclic ethane-bridged bis-sulfoxides tested, the ligand Ferbisox (11), bearing ferrocenyl moieties as substituents at the sulfinyl sulfurs, has exhibited the best results in terms of chemical yield (up to 96%) and enantioselectivity (up to 97% ee). The conjugate addition takes place smoothly in toluene at room temperature in short reaction times (typically 2 h). The reaction scope, including the use of different boronic acids, five-, six-, and seven-membered cyclic enones, an unsaturated lactone, and the most challenging acyclic ketones, is reported. An X-ray diffraction study of the [Ferbisox·RhCl]2 precatalyst clearly exhibits a dimeric structure with an S coordination of the sulfoxide to rhodium. On the basis of the X-ray data and on structural studies conducted in solution by (1)H NMR, a model explaining the high enantioselection observed is proposed.

"Sulfolefin": highly modular mixed S/olefin ligands for enantioselective Rh-catalyzed 1,4-addition.

Reported is a single high yielding step approximation to mixed olefin/sulfinamide ligands enclosing a chiral sulfur atom as the sole chiral center. The synthetic design is validated by a rapid optimization of the substituent at the sulfinyl sulfur, and by the synthesis of an efficient, highly enantioselective catalyst for the Rh-catalyzed 1,4-addition of boronic acids to both, cyclic and acyclic olefins.

Photovoltaic activity of layered zirconium phosphates containing covalently grafted ruthenium tris(bipyridyl) and diquat phosphonates as electron donor/acceptor sites.

Two layered zirconium phosphates containing Ru(bpy)(3)(2+) mono- or diphosphonates and diquat, {Ru(bpy)(3)(2+)[]/ZrP/DQ(++)} and Ru(bpy)(3)(2+)[]/ZrP/DQ(++), covalently attached to the phosphate layers exhibit notable photovoltaic response (the maximum V(OC), J(SC), and FF were 0.093 V, 16.8 microA cm(-2) and 0.33, respectively). The photocurrent spectra indicate that the photovoltaic response is due predominantly to direct photoexcitation of gamma-ZrP host, Ru(bpy)(3)(2+) and diquat acting as hole and electron traps, respectively, for the charge separated state of the semiconductor.