66350-83-2Relevant academic research and scientific papers
trans-dihalogenotitanium(IV) porphyrins, cis-disubstituted analogues, and titanium(III) derivatives. Characterization and structural investigations combining X-ray crystallography and difference EXAFS spectroscopy
Marchon, Jean-Claude,Latour, Jean-Marc,Grand, André,Belakhovsky, Michel,Loos, Michel,Goulon, José
, p. 57 - 67 (2008/10/08)
Dihalogenotitanium(IV) tetraphenylporphyrins [(TPP)TiIVX2] and octaethylporphyrins [(OEP)TiIVX2] were prepared by reaction of the appropriate hydrogen halide HX (X = F, Cl, Br) with the parent oxotitanium(IV) complex. Similarly, the reaction of the titanyl porphyrin complexes with catechol or 3,4-toluenedithiol afforded cis-disubstituted derivatives: [(TPP)TiIV(-O-)2Ph] (5) and [(TPP)TiIV(-S-)2Tol] (6). Zinc amalgam reduction of [(TPP)TiIVF2] (2) yielded the mononuclear titanium(III) complex [(TPP)TiIIIF] (7), whereas the anionic species [(TPP)TiIIIF2]- (8) was prepared by electrochemical reduction of 2 or by fluoride addition to 7. The structure of 2 was determined by single-crystal X-ray diffraction: [(TPP)TiIVF2] crystallizes in the tetragonal 14/m space group with Z = 2, a = 13.350 (1) ?, and c = 9.738 (2) ?. The structure was refined to Rw = 0.043. The complex features a trans configuration of the two fluorine atoms with D4h symmetry and strict planarity of the porphyrin core. Typical bond lengths are Ti-N = 2.040 (4) ? and Ti-F = 1.788 (4) ?. XAFS spectra were recorded at the titanium K-edge for the series [(TPP)TiIVO], [(TPP)TiIVX2], [(TPP)TiIV(-O-)2Ph], [(TPP)TiIV(-S-)2Tol], [(TPP)TiIIIF2]-, and [(TPP)TiIIIF].1 Conventional data analyses failed to give satisfactory structural data due to destructive interferences resulting in ill-posed numerical problems. However, it was possible to extract reliable structural information by resorting to perturbed difference analyses, which take into account first-order distortions such as an axial shift of the metal. Interatomic distances between titanium and the axial ligands could be extracted with an absolute uncertainty of 0.02 ? and were in excellent agreement with the available crystal structure data.
