Synthesis and Reactivity of Iridium and Rhodium Silyl Complexes Supported by a Bipyridine Ligand

The rhodium and iridium complexes [(^tBu₂bpy)₂M(μ-Cl)]₂ (M = Rh (1), Ir (2)) containing the bidentate ^tBu₂bpy (4,4′-di-tert-butyl-2,2′-bipyridyl) ligand were prepared. Dimeric complexes 1 and 2 react with HSiPh₃ to give [(^tBu₂bpy)MH(SiPh₃)(μ-Cl)]₂ in good yields (M = Rh (3) 92%, Ir (4) 90%). Addition of PⁱPr₃ to 3 or 4 gave monomeric crystalline complexes of the type (^tBu₂bpy)MH(SiPh₃)Cl(PⁱPr₃) (M = Rh (7) and Ir (8)), which adopt a slightly distorted octahedral coordination geometry with the ^tBu₂bpy ligand occupying sites trans to the hydride and chloride ligands, as determined by X-ray crystallography. Salt metathesis reactions of 7 and 8 produced (^tBu₂bpy)MH(SiPh₃)(R)PⁱPr₃ as monomeric octahedral complexes with the ^tBu₂bpy ligand occupying sites trans to the hydride and R substituents (M = Rh, R = H (11) and M = Ir, R = H (12), Me (14), and Ph (15)). Salt metathesis reactions with 3 and 4 also generated the dimeric, dicationic complexes [(^tBu₂bpy)M(SiPh₃)(μ-H)]₂[B(C₆F₅)₄]₂, where M = Rh (16) or Ir (17). Thermolysis of 15 at 100 °C in C₆H₆ for 1 day produced 12 and Ph₄Si in 47% yield, and heating 15 in the presence of 1 equiv of HSiR₃ (R = Ph, Et) also gave 12, as well as the Si−C coupled product PhSiR₃ in >95% yield.