Water-soluble and halogen-free hexaammine complexes of metal ions of group9 - Synthesis, crystal structures, and vibrational spectra

Reaction of [M(NH3)(6)]Cl-3 (M = CO, Rh, Ir) and [Ir(NH3)(5)(OH2)]Cl-3 with (NH4)(2)C2O4.H2O in aqueous solution resulted in the isolation of [M(NH3)( 6)](2)(C2O4)(3). 4H(2)O and [Ir(NH3)(5)(OH2)](2)(C2O4)(3). 4H(2)O, respecti vely. The complexes have been characterized by X-ray crystallography, IR an d UV/VIS spectroscopy. The isomorphous compounds crystallize in the orthorh ombic space group Pnnm (No. 58). Four molecules of crystal water are involv ed in an extended three-dimensional hydrogen bonding network. The libration al modes of the lattice water around 600 cm(-1) allow the characterization of [Ir(NH3)(6)](2)(C2O4)(3). 4H(2)O and [Ir(NH3)(5)(OH2)](2)(C2O4)(3). 4H(2 )O, respectively, by IR spectroscopy. The band around 600 cm(-1) shows a si gnificant frequency shift in the IR spectra of the hexaammine and aquapenta ammine complex of iridium(III) and,by that, a distinction is possible.