THE IR, NMR (H-1, C-13) AND ELECTRONIC-SPECTRA OF THE COMPLEXES CIS-[RH(CO)2(PYRIDINE-N-OXIDE)(X)] (X-EQUIVALENT-TO-CL, BR)

The complexes cis-[Rh(CO)2(PYO)(X)] (X = Cl, Br; pyO, pyridine-N-oxide ) and their labelled analogues containing (CO)-C-13 and pyO-d5 were sy nthesized. The isotopically labelled species were used to assign the i nternal ligand modes and the skeletal vibrations in the IR spectra ove r the range 4000-50 cm-1. The nuRhC and nuRhO bands occur within the r ange 400-500 cm-1, while nuRhCl and nuRbBr occur at 310 and 213 cm-1 r espectively. The H-1 and C-13 nuclear magnetic resonance spectra are d iscussed. The electronic spectra reveal a strong, broad band at 271 nm which is assigned to the combined X- --> Rh+, pi --> pi (CO) and pi --> pi (pyO) transitions, while the somewhat weaker band at 327 nm or iginates in the 4d(Rh) --> pi(CO) transition.