Edited by RALPH K. BIRDWHISTELL
textbook forum
University of West Florida Pensacoia. FL 32504
A Widespread Error in the d6 Tanabe-Sugano Diagram Anne L. Hormann and C. Frank Shaw Ill
University of Wisconsin-Milwaukee Milwaukee. Wi 53201
A recent examination in advanced inorganic chemistry brought to light a widespread error in the Tanahe-Sugano diagrams for the dhelectron configuration of octahedral complexes. The error arises with the free ion term giving rise to the strong-field (low-spin) ground state and other excited states. Four common references and texts show the origin to , be a 3D term correlated to 'At (ground state), 'TI,, ' ~ 2 'E,, and 'A?,. The strong-field sinalet states should arise from a singlet-Free-ionterm, and the'hegeneracies (15 for the putative free-ion state and 10 for the low-spin states) do not match. The confusion can be traced back to the original diagram of Tanahe and Sugano' where the II, 3D, and 'G terms are grouped together-on the vertical axis. On casual inspection the strong-field singlet states appear to originate from the 3D term instead of the 'I. A correct diagram2 is shown in the figure with the 'I giving rise to the six low-spin states 'Ag (ground state), and ITzg,'Tpg, 'Eg, and 'A2,, which account for the total degeneracy ([ZS 11X [2L 11 = 13)expected for the 'I free ion term.
+
+
' Tanabe, Y.; Sugano, S. J. Phys. Soc. (Japan) 1954,9, 766.
Purcell. K. F.; Kotz. J. C. horganic Chemistry. Saunders: Philadelphia, 1977: p 585.
918
Journal of Chemical Education
A
correct Tanabe-Sugano diagram2for the de configuration. (Copyright by permission.)
W.B. Saunders Co. and used with
