Stoichiometric and Catalytic Reactions Involving Si−H Bond Activations by Rh and Ir Complexes Containing a Pyridylindolide Ligand

New rhodium and iridium complexes containing the bidentate, monoanionic 2-(2‘-pyridyl)indolide (PyInd) ligand were prepared. The bis(ethylene) complex (PyInd)Rh(C 2 H 4 ) 2 ( 3 ) reacted with triethylsilane at 60 °C to produce the 16-electron Rh(V) bis(silyl)dihydride complex (PyInd)RhH 2 (SiEt 3 ) 2 ( 4 ). Both 3 and 4 catalyzed the chloride transfer reaction of chlorobenzene and Et 3 SiH to give Et 3 SiCl and benzene in the absence of base. In the presence of LiN i Pr 2, catalytic C−Si coupling was observed, to produce Et 3 SiPh. Analogous Ir complexes of the type (PyInd)IrH 2 (SiR 3 ) 2, where R 3 = Et 3 ( 6a ), Me 2 Ph ( 6b ), Ph 2 Me ( 6c ), or Ph 3 ( 6d ), were not catalytically active in this chloride transfer chemistry. The molecular structure of 6c, determined by X-ray crystallography, may be described as having a highly unusual bicapped tetrahedral geometry. DFT calculations indicate that this distortion is associated with the d 4 electron count and the presence of highly trans -influencing silyl ligands. The reaction of 6a with PMe 3 (5 equiv) produced (PyInd)IrH(SiEt 3 )(PMe 3 ) 2 ( 7 ), while the reaction with PPh 3 (1 equiv) generated a mixture of isomers that was converted to (PyInd)IrH(SiEt 3 )(PPh 3 ) ( 8 ) upon heating in benzene at 80 °C. Complexes 7 and 8 exhibit regular octahedral and distorted square pyramidal geometries, respectively.