METAL-LIGAND COOPERATION WITH NHC-PHOSPHONIUM YILDE PINCER COMPLEXES

Work package:
Among the large variety of ligands available, carbon ligands have become essential, especially with the emergence of N-heterocyclic carbenes (NHC). Phosphonium ylides (PY: R3P+−CR2− <-> R3P=CR2), which represent an alternative class of carbon ligands act also as effective Lewis bases in coordination chemistry. Electron-rich NHC-phosphonium ylide Pd(II) complexes were thus recently prepared in the bidentate (A),1 and in the pincer series (B),2 the latter being active in the catalytic allylation of aldehydes. In parallel, a bidentate NHC-based Mn(I) complex (C) featuring a phosphonium ylide (PYr) bound in a reversed fashion to the metal was reported to activate H2 through a new mode of metal-ligand cooperation acting as one of the most efficient catalyst for ketone hydrogenation.3 More recently, an ortho-metalated Pd(II) complex (D) containing such P-coordinated phosphonium ylide was characterized.4 Based on these results, it is envisioned now to prepare unprecedented pincer complexes E exhibiting NHC ligand N-substituted by two phosphonium ylides, one ylide being bound to the metal in a conventional manner by its C- atom to provide strong electron density and the other one in an unconventional manner by its P-atom to bring non-innocent character. The synthesis of complexes E that maintain a vacant coordination site could constitute a step forward in the design of new cooperative carbon-based systems, from a fundamental point of view but also in the perspective of catalytic applications (See corresponding illustration as attached file). We are looking for a motivated candidate for this internship, which will take place in the team “Molecular design of transition metal pre-catalysts” of the LCC-CNRS in Toulouse. The realization of this internship will allow the candidate to acquire expertise in synthetic organometallic chemistry, organic synthesis, homogeneous catalysis and various spectroscopic methods.