Trichlorostannyl complexes of iridium with both P-donor and N-donor ligands: Preparation and activity as hydrogenation catalysts

Bis(trichlorostannyl) complex IrH(SnCl3)2(PPh3)2 (1) was prepared by allowing the chloro-derivative IrHCl2(PPh3)3 to react with SnCl2·2H2O in ethanol. Instead, treatment of phosphite complexes IrHCl2P3 [P = P(OEt)3 and PPh(OEt)2] with SnCl2·2H2O gave stannyl derivatives IrCl2(SnCl3)P3 (2). Pyrazole–trichlorostannyl complexes IrHCl(SnCl3)(HRpz)P2 (3, 4) (R = H, 3-Me; P = PPh3, PiPr3) were prepared by allowing chloro-derivatives IrHCl2(HRpz)P2 to react with SnCl2·2H2O. 1,2-Bipyridine-trichlorostannyl complexes IrHCl(SnCl3)(bpy)P (5) (P = PPh3, PiPr3) were also prepared. Complexes 1–5 were characterised spectroscopically (IR, 1H, 31P, 119Sn NMR) and a geometry in solution was also established. The trichlorostannyl iridium complexes were evaluated as catalyst precursors for the hydrogenation of 2-cyclohexen-1-one and cinnamaldehyde. The influence of the stannyl group, as well as the steric hindrance of both N-donor and P-donor ligands in the catalytic activity of the complexes is discussed.