Ligand Site Exchange Induced by Intrametallic Rearrangement Processes in H₂FeRu₃(CO)_13-x(PR₃)_x (x = 1, 2)

The fluxional processes which occur in H₂FeRu₃(CO)₁₂L (L = PMe₂Ph, PMe₃) and H₂FeRu₃(CO)₁₁L₂ (L = PMe₃, PPh₃, P(OMe)₃, P(OEt)₃) have been studied by a combination of variable-temperature ¹H, ³¹P, and ¹³C NMR spectroscopy. The fluxional processes are basically the same as those which have been shown to occur in the unsubstituted H₂FeRu₃(CO)₁₃ cluster and involve bridge-terminal CO exchange localized on Fe, cyclic exchange of the carbonyls about the triangular face of the cluster which possesses the bridging CO's, and rearrangement of the metal framework with a corresponding shift of the hydrides and carbonyls. The intrametallic rearrangement process is of profound importance in these substituted derivatives since it leads to exchange of the substitution sites. For the monosubstituted derivatives, this exchange leads to the facile C_s↔C, isomerization observed, and for the disubstituted derivative it renders the phosphorus donor ligands equivalent on the time scale of the NMR measurements.