AN IR-193 AND AU-197 MOSSBAUER INVESTIGATION OF IRIDIUM(I), IRIDIUM(III) AND IRIDIUM(I) GOLD(I) COMPLEXES

Comparison of the Ir-193 and Au-197 Mossbauer spectra of the series trans-(Ph3P)2Ir(CO)X, trans,cis-(Ph3P)2(H)2Ir(CO)(X) (X = Cl or pz-N; pzH = 3,5-dimethyl-, 3,5-dimethyl-4-nitro-, 3,5-bis(trifluoromethyl)pyrazole) and trans-(Ph3P)2(CO)Ir[mu-(3,5-dimethylpyrazolato-N,N')]AuX' (X' = Cl, Br) shows that even the substituents on the heterocycle influence the electron density at the iridium nucleus and that the bridging pyrazolato ligand transmits electronic effects from gold to iridium through three bonds. The Mossbauer parameters are sensitive to the ligand X but not to the presence of conformers.