Some selected chapters from the (butadiene)zirconocene story

(Butadiene)zirconocene was the first mono-nuclear metal complex for which the s-trans-η4-conjugated diene coordination mode was established. Meanwhile a variety of additional examples from metals throughout the Periodic Table was found. The (butadiene)zirconocenes have found use as valuable reagents in organic and organometallic synthesis, for which various representative examples are described. They have also found extensive use as precursors for the generation of very active and sometimes very selective homogeneous metallocene Ziegler–Natta olefin polymerization catalysts. The employment of the dipolar zirconocene(butadiene)/B(C6F5)3 addition products in mechanistic studies has revealed important aspects of the reaction course taken in the carbon–carbon coupling reaction sequences at this important class of catalysts. Several specific examples are described in this article.