P(⁶-C₆H₆)₃ does not exist. You have confused C₆H₅ (phenyl) and C₆H₆ (benzene). Phenyl groups form 1 bond to another electron. Phosphorous has 5 valence electrons, s²p³, and can not -bond to 3 benzene rings. Each ring would then supply 6e^- to the phosphorous exceding its lectrons requirements for a full shell. As drawn the C-5 ring would be C₅H₄ and only give 1e^- (¹). This is wrong. For stability C₅H₄ need giving all 5e- (⁵). Fe bonds to all the carbons in the ring.
 

Fe      = 8e- C5H4 = 1e- COT  = 2e- CH3   = 1e- PPh3  = does not exist

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