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.