Rearrangement of coordinated ligands on a metal framework

The interaction between hydride and ylide ligands in the complex, [W(H)(CH2=PMe2Ph)Cp2][PP6], has been studied.57 On heating in acetone, the complex is transformed into [W(Me)(PMe2Ph)Cp2)[PF6]. Based on kinetic studies, two alternative mechanisms for the rearrangement were proposed. One involves the formation of an agostic methyl intermediate, [W(CH2)(p-H)Cp2], and the other involves an equilibrium between a carbene hydride, [W(CH2)(H)Cp2]+, and a methyl cation, [W(CH3)Cp2] 

In boiling toluene this transformation occurs over five days in a yield of 58%. 

Transfer of coordinated triphenylphosphine to a carborane ligand, accompanied by hydride transfer from the carborane to the metal center, has been observed in nickel(II) complexes, Eq. 11.6  

The resulting carborane ligand is present in the phosphonium form. The rearrangement takes place on prolonged heating in inert solvents. 

Transfer of the pentamethylcyclopentadienyl group from phosphorus to nickel and loss of one of the tertiary phosphine ligands, yielding [Ni(P=NBuO(PBu3)Cp ], occurs when the temperature is increased to -5 C.60 

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