Département de chimie moléculaire

The modelization of phosphine ligands commonly used in inorg. and organometallic chem. as for example the asym. Pauson-Khand reaction by ONIOM method are discussed. A fundamental question that arises after the decision of using QM/MM methods for a certain study is how to partition the system. Which atoms are going to be included in the QM region and which atoms are going to be included in the MM region Chem. knowledge is most of the time the guiding line for this choice, but tests should be run in case of uncertainty. For the setting of the QM/MM border, 2 criteria have been employed: results from geometry optimizations of the ligand complexed to W penta(tetra)carbonyl and calcns. of the mol. electrostatic potential (MESP) for the ligand alone. These 2 methods give similar conclusions and thus MESP can be used to validate the ONIOM partition of these systems. This later approach has the advantage of being fast and computationally inexpensive. [on SciFinder(R)]