MECHANISM FOR THE EXCHANGE PROCESSES OBSERVED IN THE COMPOUNDS [M(ETA-C5H5)2(ETA-RCH=CH2)H] (M = NB, TA)

The fluxional processes in the compounds exo-[M(eta-C5H5)2(eta-CH3CH=CH2)H] (M = Nb, Ta) have been investigated by magnetization and spm-saturation transfer and two-dimensional exchange NMR techniques. Rate constants for three separate processes have been determined. A mechanism involving agostic eta-2-alkyl ligands is proposed.