Effect of N-Methylation of Macrocyclic Amine Ligands on the Spin State of Iron(III): A Tale of Two Fluoro Complexes
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- 作者：John F. Berry ; Eckhard Bill ; Ricardo Garcí ; a-Serres ; Frank Neese ; Thomas Weyhermü ; ller ; and Karl Wieghardt
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：March 6, 2006
- 年：2006
- 卷：45
- 期：5
- 页码：2027 - 2037
- 全文大小：211K
- 年卷期：v.45,no.5(March 6, 2006)
- ISSN：1520-510X
文摘
Syntheses and characterization of [(cyclamacetate)FeF]PFB>6 (1) and the corresponding N-methylated complex[(trimethylcyclamacetate)FeF]PF6 (3) are presented. Compound 1 is prepared in good yields from the analogouschloro complex, whereas 3 is prepared by hydrolysis of the oxo-bridged diiron compound (Me3cyclam-acetate)Fe-O-FeCl3 (2) in the presence of PF6 anions. Magnetic susceptibility and spectroscopic data including electronparamagnetic resonance and Mössbauer spectra indicate that 1 contains low-spin FeIII (S = 1/2), while 3 is highspin (S = 5/2). Both octahedral fluoro complexes were investigated theoretically by density functional theory inorder to determine why the spin states of the two molecules are different. Energies calculated using the B3LYPfunctional correctly predict 1 to have a low-spin S = 1/2 ground state and 3 to be high spin, regardless of whethera solvation model is included. The difference between 1 and 3 is most likely a combination of steric effects causedby the N-methyl groups, which compel the Fe-N bond distances to be longer in 3 than they ordinarily would be,and also electronic effects, which cause the N-methylated ligand to be a weaker 
donor than its nonmethylatedcounterpart.
donor than its nonmethylatedcounterpart.