INFRARED SPECTRA AND METHYL GROUP PROPERTIES IN DICYCLOPENTADIENYLDIMETHYL-TITATIUM(IV), -ZIRCONIUM(IV) AND -HAFNIUM(IV)

Article abstract of DOI:10.1016/0022-328X(86)80297-2

Infrared spectra are reported for CH3-, CD3-, and CHD2-substituted Cp2MMe2 (Cp = η⁵-C5H5, M = Ti, Zr, Hf) in CCl4 solution.The isolated CH stretching frequencies, ν(^isCH), measured in the CHD2 species are lower than any previously observed in methylmetal compounds and the methyl CH bonds in Cp2HfMe2 are predicted to be the longest and weakest such bonds yet to have been characterised by this method.The methyl groups in Cp2ZrMe2 and Cp2HfMe2 have all three CH bonds equal, but in Cp2TiMe2 each methyl group contains two strong CH bonds and one weak one.This may be the result of steric overcrowding effects around the relatively small titanium atom.The symmetric deformation δ_s(CH3) rises with increasing atomic number of the metal atom, the reverse of the trend observed for methyl derivatives of Main Group elements.