
%0 Journal Article
%A Ho, RKY 
%A Livingstone, SE 
%T Thio derivatives of &#946;-diketones and their metal chelates. X. The anomalous paramagnetism of some iron(III) chelates of monothio-&#946;-diketones
%J Australian Journal of Chemistry
%D 1968/08/01
%V 21
%N 8
%P 1987-1996
%K 
%R https://doi.org/10.1071/CH9681987
%U https://www.publish.csiro.au/paper/CH9681987 
%X The magnetic susceptibilities of the iron(111) chelates Fe(R1CS=CHCOR2)3 (R1 = Ph, p-MeC6H4, p-MeOC6H4, p-BrC6H4, 2-thienyl, 2-furyl, R2 = CF3; R1 = Ph, R2 = Ph, OEt) have been investigated over a temperature range. The iron(111) complex of ethyl thiobenzoylacetate (R1 = Ph, R2 = OEt) is of the high-spin type and obeys the Curie-Weiss law with &#952; =-8ºk. The moments of the other complexes vary between 2.31 and 6.61 B.M. at room temperature and are temperature-dependent, ranging from 1.86 to 4.07 B.M. at 80ºk, depending on the nature of R1 and R2 This behaviour is postulated to be due to a thermal equilibrium between the nearly equi-energetic spin-paired (t5/2g) and spin-free (t3/2ge2/g) configurations of the iron atom, resulting from the approximately equal magnitudes of the ligand field (&#916;) and the pairing energy (&#960;) in these complexes. The ligand field and consequently the magnetic behaviour are sensitive to the nature of R1 and R2: electron-withdrawing groups appear to be the most effective in increasing the population of the spin-paired configuration. 
