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Hu C, Noll BC, Scheidt WR: Sulfoxide as a ligand in iron (II) porphyrinates: S- or O-bound? . Inorg Chem. 2007 Oct 1;46(20):8258-63. Epub 2007 Sep 8.
In order to study the bonding of sulfoxides to iron (II) porphyrinates, an equilibrium study of Fe (TPP) with tetramethylenesulfoxide (TMSO) has been performed. UV-vis spectra at different concentrations of TMSO have shown distinct character belonging to three species: four-coordinate Fe (II)(TPP), five-coordinate [Fe (II)(TPP)(TMSO)], and six-coordinate [Fe (II)(TPP)(TMSO) 2]. The isosbestic points for the low TMSO concentrations suggest that the equilibrium constant K1 is much larger than K2. Analysis of spectral data by the nonlinear least-squares program SQUAD gives K1 = 267 and K2 approximately 1. Even though the five-coordinate species is the dominant species under the synthetic conditions, only the six-coordinate species was crystallized and characterized by an X-ray diffraction study. [Fe (TPP)(TMSO) 2] (C52H44Fe-N4O2S2): monoclinic, P2 (1)/c, a = 11.2580 (3) A, b = 15.9262 (5) A, c = 12.3930 (4) A, beta = 116.246 (1) degrees , V = 1992.95 (10) A3, Z = 2. X-ray crystallography demonstrates the complex is a low-spin bis-TMSO ligated species. The average Fe-Np distance is 1.999 (4) A. The most important feature is that TMSO is coordinated to iron (II) by the sulfur donors, not oxygen. The Fe-S distance is 2.2220 (3) A. |
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