Hydrido-1,5-cyclooctadieneiridium(III) complexes stabilized by trichlorostannate ligands and the structure of [IrH2(SnCl3)(PPh3)3]

The complexes [IrH(SnCl3)2(1,5-COD)L], [IrH2(SnCl3)(1,5-COD)] and [IrH2(SnCl3)L3], L = tertiary arylphosphine, have been isolated characterized by 1H, 31P and 119Sn NMR spectroscopy. The coordinated 1,5-COD ligand is stable with respect to insertion into an iridium-hydride bond at room temperature, in contrast to the cationic complexes [IrH2(1,5-COD)L2]+ which are known to react rapidly at this temperature. The complexes [IrH2(SnCl3)(1,5-COD)L] exist as cis,cis- and cis,trans- (L trans to SnCl3 -) isomers in solution. [IrH2(SnCl3)(1,5-COD)(PPh3)] is a poor hydrogenation catalyst for the olefins styrene, cyclohexene and 1,5-COD at room temperature in CH2Cl2. The structure of [IrH2(SnCl3)(PPh3)3] has been determined by crystallographic methods. The three phosphines are in a pseudo-meridional arrangement and the two hydrides are cis to one another. The phosphine ligands are displaced toward the hydrido ligands relative to their position in a typical octahedral complex. Relevant bond lengths (Å) and bond angles (°) are as follows: IrSn, 2.623(1); IrP, 2.318(4), 2.340(4), 2.395(3) (with the latter for P trans to H); SnIrP, 97.54(10), 97.35(9), 99.97(9); PIrP, 102.11(12), 105.21(11), 145.95(9) (P trans to P). The hydride ligands have been located at a distance of ca. 1.7 Å from the metal.