The organometallic chemistry of cycloheptatrienyl zirconium complexes

Abstract

This tutorial review summarizes the organometallic chemistry derived from the half-sandwich complex [(η⁷-C₇H₇)ZrCl(tmeda)], which was used as an efficient and versatile starting material for the incorporation of monoanionic ligands into the cycloheptatrienyl zirconium coordination sphere by conventional salt metathesis reactions. A broad variety of ligands was employed, affording novel and previously inaccessible cycloheptatrienyl (sandwich) complexes of the type [(η⁷-C₇H₇)Zr(Y)]; Y comprises pentadienyl, cyclopentadienyl, allyl, phospholyl, boratabenzene, imidazolin-2-iminato and amido systems. The cycloheptatrienyl ring in these systems usually acts as an “innocent spectator ligand”, but reactivity can arise from the second ligand Y or the Lewis acidity of the, formally, Zr(+IV) center, which was probed in selected examples and put in perspective to related studies. The corresponding results emphasize why the use of [(η⁷-C₇H₇)ZrCl(tmeda)] is clearly an advancement in the chemistry of the still fairly unexplored area of cycloheptatrienyl transition metal complexes.