Metal variation with fixed ancillary-ligand set

2 Metal variation with fixed ancillary-ligand set 

In contrast to an E-H fragment, where variation in the main-group element E simply changes the frontier orbital populations, changes in metal identity for a L M 

Exercise 4.5. Count the skeletal electron pairs (or cluster valence electrons) in the organometallic complex shown below at the left. Is there a relationship to cyclobutadiene iron tricarbonyl shown next to it  

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