Hybrid Phosphine/Amino-Acid Ligands Built on Phenyl and Ferrocenyl Platforms: Application in the Suzuki Coupling of o-Dibromobenzene with Fluorophenylboronic Acid.

We describe the synthesis and characterization of two classes of hybrid phosphino ligands functionalized with amino ester or amino acid groups. These compounds are built either on a rigid planar phenyl platform or on a functionalized - conformationally controlled - rotational ferrocene backbone. Modifications at the -PR phosphino groups (R=aryl and alkyl, with various steric bulk, Ph, Mes, i-Pr, Cy) and at the amino acid/amino ester functions are reported, showing a valuable high modularity.

Palladium complexes of N-heterocyclic carbenes displaying an unsymmetrical N-alkylfluorenyl/N'-aryl substitution pattern and their behaviour in Suzuki-Miyaura cross coupling.

A series of new Pd-PEPPSI complexes containing imidazolylidene ligands with a mixed 9-alkyl-9-fluorenyl/aryl N,N'-substitution pattern have been synthesised. Single crystal X-ray diffraction studies were carried out for four complexes, which revealed that the N-heterocyclic carbene ligands display a semi-open, unsymmetrical space occupancy about the metal. Despite their particular unsymmetrical shape, the new complexes were found to perform as well in Suzuki-Miyaura cross coupling (dioxane, 80 °C) as previously reported, highly active analogues bearing two sterically protecting 9-alkylfluorenyl substituents.