Synthesis and characterization of tetrairon–tungsten cluster complex containing a μ4, η2-carbonyl ligand

Reaction of [(PPh2C5H4)Cp3Fe4(CO)4] (1) with (CO)4W(CH3CN)2 at ambient temperature affords [(CO)4W(PPh2C5H4)Cp3Fe4(CO)4] (2) as the major product, together with a small amount of [(CO)5W(PPh2C5H4)Cp3Fe4(CO)4] (3). Compound 3 can be obtained in good yield by treating (CO)5W(CH3CN) with equal molar of 1, and reaction of 3 with Me3NO in acetonitrile solvent produces 2 exclusively. The crystal structures of 2 and 3 have been determined by an X-ray diffraction study. Compound 2 contains an interesting μ4, η2-CO ligand, where two electrons donated by the carbon atom are involved to bridge a Fe3 face and two electrons from oxygen are donated to the tungsten(0) atom.