The different binding modes of p-anisaldehyde to the [TpMo(CO)(MeC=CMe
)](+) and [TpW(CO)(MeC=CMe)](+) fragments in solution have been assess
ed by IR and H-1 and C-13 NMR spectra. X-ray analyses substantiate tha
t p-anisaldehyde is a-bound in, the molybdenum complex 1 and pi-bound
in the tungsten complex 2.