BULKY OR SUPRACYCLOPENTADIENYL DERIVATIVES IN ORGANOMETALLIC CHEMISTRY

This chapter focuses on supracyclopentadienyl derivatives in organometallic chemistry. Within organometallic chemistry—synthetic, analytical, physical, applied, and theoretical chemists are involved in research projects, dealing with highly substituted cyclopentadienylide (Cp)-metal complexes. Supra-Cp's are a major focus of this chapter, whereas for many others they are just a sideline where the bulkiness is a minor feature in the comparative study of certain phenomena. This chapter reveals unifying interest, sometimes with no cross-referencing to similar bulky Cp systems or even different metals carrying the same supra-Cp. The basic bulky Cp systems that are common in organometallic chemistry are discussed in the chapter, in their anionic form as ball-and-stick models with the hydrogens included. Other basic bulky Cp's described in the chapter are di(isobutyl)(tert-buty1)-Cp, penta(isopenty1)- Cp [isopentyl=( H,C2)2CH-], and tris(methoxycarbony1)-Cp. This chapter presents highly substituted Cp's, supracyclopentadienes that so far have escaped attention as ligands in organometallic complexes: tetra(terfbuty1)- Cp, 3,Mimethyl- and 3,5di-n-propyl- 1,2,4-triphenyl-Cp, and 1,2,3,5-tetraphenyl-4-p(7-cycloheptatrienyl)phenyl-Cp. Most of the bulky ring substituents are simple hydrocarbon moities, either alkyl or aryl groups, and consequently the supra-Cp's can be divided into two classes: peralkyl and peraryl systems. The use of bulky cyclopentadienes with functional group substituents causes problems in organometallic synthesis. Although there is a sizable number of Cp- metal complexes with only one functional group on the Carbon, ring examples for persubstituted systems are limited. This chapter also covers tetrasubstituted fulvalenes ethylene-bridged bis(tetrahydroindeny1) complexes and a dibornacyclopentadienyl ligand. © 1991 Academic Press, Inc.