Fluorinated N-heterocyclic carbenes rhodium (I) complexes and their activity in hydrosilylation of propargylic alcohols

The synthesis of three rhodium complexes with fluorinated N-heterocyclic carbenes of general formula [RhCOD(NHC)Cl] where COD = 1,5-cyclooctadiene, NHC = N-heterocyclic carbene [1-butyl-3-pentafluorobenzyl-imidazol-2-ylidene (1), 1-benzyl, 3-pentafluorobenzyl-imidazol-2-ylidene (2) and 1,3-Bis(pentaflurobenzyl)-imidazol-2-ylidene (3)], and their respective NHC ligands as imidazolium salts are reported. The catalytic activity in hydrosilylation of two propargylic alcohols gives mainly isomers E and gem; however when cationic form of the catalysts with triphenylphosphine as an additional ligand are used, only the E isomer is observed for all the complexes. The x-ray structures of two complexes (1 and 2) show square planar geometries with rhodium-carbene bond lengths in the short range 2.025(5)-2.028(5) Å indicating little influence of the NHC’s arms.