INFRARED-SPECTRUM OF CYCLOPENTADIENYLTRIMETHYLTITANIUM(IV) AND INVESTIGATION OF THE METHYL-GROUP GEOMETRY THROUGH PARTIAL DEUTERATION STUDIES

Infrared spectra have been recorded between 4000 and 200 cm(-1) for cy clopentadienyltrimethyltitanium(IV) in the forms CpTi(CH3)(3), CpTi(CH 2D)(3), CpTi(CHD2)(3), and CpTi(CD3)(3) (Cp = eta(5)-C5H5); measuremen ts have been made (i) on the molecules isolated in solid N-2 matrices at 14 K, (ii) on solutions of the compounds at room temperature, and ( iii) on the annealed solid condensates at 77 K. Vibrational fundamenta ls of the TiMe(3) fragment have been identified with particular refere nce to the v(CH) and v(CD) modes, which have been analyzed in terms of a harmonic local mode force field. The spectroscopic evidence is that the methyl groups, while unexceptional in their gross geometry, are a symmetric: with the molecule in the matrix-isolated or solution states , they feature one strong and two weak C-H bonds, but the pattern chan ges to one weak and two strong C-H bonds for the solid. The results of fer a basis for comparison with the properties of other methyltitanium compounds, as well as a test of the utility of ''isolated'' C-H and C -D stretching frequencies. On the basis of the analysis, an alpha-''ag ostic'' Ti ... H-C interaction is proposed.