Complexes of the 4d- and 5d-Groups. I. Crystal Field Spectra of Rhodium(III) and Iridium(III).

Abstract

In octahedral complexes with six d-electrons and singlet (i. e. diamagnetic) ground state, the crystal field theory predicts transitions to two singlet and two triplet levels.\tSeveral authors have studied the case of cobalt(Ill), and in this paper the four bands are found in rhodium(III) and iridium(III) complexes, e. g. with six bromide or chloride ligands. The slow aquation of these complexes in HCI and HClO4. is studied, and rhodium(III) aquo ions prepared in HClO4. The solutions of Rh(OH)3 in acids show a high ultraviolet absorption, which disappears slowly, presumably owing to acidolysis of polymer hydroxo complexes. The hexammine and nitro-, iodo-, bromo-, chIoro-, hydr.. 0%0-,- and.aquo-pentammine rhodium complexes of S. M. Jergensen, and the oxalato and ethylenediamine complexes exhibit :the shifts predicted from the spectrochemical series, as also Ir(NH.),Cl+ + and Ir en.+++. The relative intensities of singlet and triplet transitions are explained by the deviations from the Russell-Saunders coupling, which are importaD:t in the heavy atoms. Later papers of the series will discuss why the concept of molecular orbitals is compatible with the approximate validity of the electrostatic modeli.lsiIlg (E1 - E2) as empirical parameter.