Tris(pyrazolyl)methane Sulfonate Complexes of Iridium: Catalytic Hydrogenation of 3,3-Dimethyl-1-butene

The synthesis and characterization of three new iridium complexes bearing a tris(pyrazolyl)methane sulfonate ligand of the type [Ir(Tpms)(LL‘)2] (L, L‘ = C2H4 1; L = C2H4, L‘ = PPh3 2; L = (H)2, L‘ = PPh3 3; Tpms = tris(pyrazolyl)methane sulfonate) have been carried out. Complex 3 catalyzes the hydrogenation of the sterically crowded 3,3-dimethyl-1-butene to 2,2-dimethylbutane under mild conditions. The mechanism of the hydrogenation reaction has been studied using the model complex [Ir(H)2(Tpms)(PH3)] (3a) by computational methods at the B3LYP/LANL2DZ level. Hydrogenation of ethylene to ethane by the model complex is exothermic by −27.1 kcal/mol.