Synthesis, structure determination, and hydroformylation activity of N-heterocyclic carbene complexes of rhodium

The effect of ancillary phosphine ligands on the structure and hydroformylation activity of Rh-N-heterocyclic carbene complexes of type [Rh(IMes)(P[R.sub.3])(CO)Cl] and [Rh(SIMes)(P[R.sub.3])(CO)Cl] is described. Very high selectivities for the branched isomer (>95:5) were obtained in the hydroformylation of vinylarenes in all cases except for R = OPh. The new complexes were characterized spectroscopically and by X-ray crystallography. Key words: hydroformylation, rhodium, N-heterocyclic carbene, IMes. On decrit l'effet des ligands phosphines d'appoint sur la structure et l'activite d'hydroformylation de carbenes complexes Rh-H-heterocyclique, du type [Rh(IMes)(P[R.sub.3])(CO)Cl] et [Rh(SIMes)(P[R.sub.3])(CO)Cl]. Dans tous les cas excepte celui ou R = OPh, des selectivites tres elevees de l'isomere ramifie (>95 : 5) ont ete obtenues lors de l'hydroformylation de vinylarenes. Les nouveaux complexes ont ete caracterises par spectroscopie et par diffraction des rayons X. Mots cles : hydroformylation, rhodium, carbene N-heterocyclique, IMes. [Traduit par la Redaction]