Zirconium alkylcyclopentadienyls carbonyls (h5-C5H4R)Zr(CO)2 are very reactive, compounds easily eliminating CO (have 18-valence electroncs), were considered as potential precursors for MOCVD.
They are synthesized by reaction of Zr alkylcyclopentadienyls with CO:
(h5-C5H4R)Zr + 2 CO → (h5-C5H4R)Zr(CO)2