The initial aim of this work was to synthesize "zirconocene" derivatives using substituted cyclopentadienyl ligand Cp^s.(Cp^s = ^-C₅Me₄(SiMe₂Bu^t)). However, the  "ZrCp^s₂Cl₂ => ZrCp^s₂Cl => ZrCp^s₂ " route was unsuccessful leading us to consider the alternative via mono-cyclopentadienyl Zr complexes.

The Zr^III complexes:

The one  mol reduction of ZrCp^sI₃ resulted a  Zr^III complex in both a dimeric and a trimeric (thermodynamic)  form.

For the chloro-analogue, only trimer was detected from the reduction of [{ZrCp^sCl₂(mu-Cl)}₂].  All these compound are stable under Nitrogen atmosphere at room temperature.

With all the iodine atoms bridged, the trimers are  rather chemically inert, e.g. , towards ligand transfer reagent such as LiCp^s. The dimer Zr^IIICp^sI₂ reacted with one equivalent of LiCp^s in toluene, but to our surprise, it worked out as a reducing agent rather than a ligand transfer reagent. [(ZrCpI)₂(C₇H₈)] was obtained after crystallization from hexane solution. The reduction was preformed using Na/Hg in toluene media and result was repeated. The compound [(ZrCpI)₂(C₇H₈)] is green, diamagnetic, sensitive to air & moisture.

The  NMR spectra (in either d⁶-Bezene or d¹²-cyclohexane) of [(ZrCpI)₂(C₇H₈)] exhibited the constancy with the solid structure. 

[(ZrCpI)₂(C₇H₈)]

structure (.res file)

view structure (.gif file)

NMR spectra (.gif file)

More reference:
arene complexes
Zr(II) complexes

Using [{Zr^IIICl₃(PBu₃)}₂] to react with two equivalent of LiCp^s, only disproportionation product was obtained.

The steric bulky [ZrCp^s₂Cl₂] cannot be synthesis from LiCp^s and ZrCl₄ with ease, but this reaction suggested  that the bis-cyclopentadienyl Zr derivatives can be access by Zr(III).

[{Zr^IIICl₃(PBu₃)}₂]: Wengrovius, J. H.; Schrock, R. R. and Day, C. S. Inorg. Chem., 1981, 20, 1844.

The structure 

[ZrCp^s₂Cl₂] (.res file)