Investigation of Dienophile-TiCl(4) Complexation by Means of X-ray Absorption and (13)C-NMR Spectroscopies.
Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) techniques, in combination with (13)C-NMR spectroscopy, have been used to study the complexation of methyl acrylate (1), N-acryloylbenzylamine (2), O-acryloyl-(R)-pantolactone (3), methyl N-acryloyl-(S)-prolinate (4), and methyl N-acryloyl-(S)-phenylalaninate (5) with excess TiCl(4) in solution. The results obtained show that TiCl(4) has a great tendency to coordinate with two ester ligands, but this tendency is not so marked with amides, which is related to the greater basicity of the latter. Complexation increases the Ti-Cl bond distance, in comparison with TiCl(4), which is clearly shown by the EXAFS spectra. Chelate complexes are formed with bidentate ligands, but comparison between the EXAFS spectra, obtained with different TiCl(4)/dienophile ratios, shows that chelation is more difficult with methyl N-acryloyl-(S)-phenylalaninate (5).
Assfeld
Xavier
X
Laboratoire de Chimie Théorique, URA-C.N.R.S. 510, Université Henri Poincaré-Nancy I, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France, and Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain.
García
Joaquín
J
García
José I.
JI
Mayoral
José A.
JA
Proietti
M. Grazia
MG
Ruiz-López
Manuel F.
MF
Sánchez
María C.
MC