Abstract
The low-temperature 1H n.m.r.spectra of the new compounds (π-C5H5)Ru(CO)2(σ-C5H4R)(R = H or Me) have been studied and those of (π-C5H5)Fe(CO)2(σ-C5H5) and (σ-C5H5)CuPEt3 have been re-examined. Satellite lines due to coupling to 13C were observed in the spectra of the compounds (π-C5H5)M(CO)2(σ-C5H5)(M = Fe or Ru) by spectrum accumulation at low temperature. The results indicate that in each of the three compounds with an unsubstituted σ-cyclopentadienyl ring the metal migrates round this ring by a sequence of 1,2-shifts. For the compounds (π-C5H5)M(CO)2(σ-C5H5)(M = Fe or Ru) the activation energies for this process were found to be 8·5 ± 0·8 and 9·6 ± 1·0 kcal. mole–1 respectively. Migration of the metal atom round the σ-bonded ring also occurs in (π-C5H5)Ru(CO)2(σ-C5H4Me) and this is discussed.
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