Introduction:
In coordination chemistry, π-bonded complexes are those in which the metal atom forms π-bonds with ligands. These complexes are characterized by the presence of metal-ligand π-bonds, which involve the donation of electron density from filled π-orbitals of the ligands to empty or partially filled d-orbitals of the metal. Let's analyze the given options to determine which one is not a π-bonded complex.

Analysis:
a) Zeise's salt: Zeise's salt, also known as potassium trichloro(ethylene)platinate(II), is a π-bonded complex. It consists of a central platinum atom bonded to three chloride ligands and one ethylene ligand through π-bonds. Therefore, option (a) is a π-bonded complex.

b) Ferrocene: Ferrocene is an organometallic compound in which an iron atom is sandwiched between two cyclopentadienyl rings. The iron atom forms π-bonds with both cyclopentadienyl rings, making it a π-bonded complex. Therefore, option (b) is a π-bonded complex.

c) Dibenzene chromium: Dibenzene chromium, also known as bis(benzene)chromium, is a compound in which a chromium atom is coordinated to two benzene ligands. The coordination between the chromium atom and the benzene ligands involves π-bonding. Therefore, option (c) is a π-bonded complex.

d) Tetraethyl lead: Tetraethyl lead is an organometallic compound in which a lead atom is bonded to four ethyl groups. The bonding between the lead atom and the ethyl groups does not involve π-bonding. Instead, it is primarily a result of σ-bonding. Therefore, option (d) is not a π-bonded complex.

Conclusion:
Among the given options, tetraethyl lead (option d) is not a π-bonded complex. It does not involve the formation of π-bonds between the lead atom and the ethyl groups. The other options, Zeise's salt, ferrocene, and dibenzene chromium, are all examples of π-bonded complexes.