Cyclopentadienyl! Cp complexes

Fig. 9 Preparation of a cyclopentadienyl (Cp) complex from water X-ray structure of [(PhCO-Cp)Tc(CO)3]...

A large number of cyclopentadienyl (Cp) complexes, both neutral and charged, has been prepared. Most of the complexes reported are for early to mid-transition metals. Rich redox and chemical reactivity has been reported (126). Extensive work on the Cp dithiolene complexes has been carried out by Sugimori et al. (127) and has recently been reviewed. A few representative examples are discussed below. 

In comparison to the allyl complexes, the analogous cyclopentadienyl (Cp) complexes, with the exception of nickelocene, Cp2Ni (see Nickelocene), have played a less prominent role. However, there has been a resurgence of interest over the past decade in the reactivities of CpNi complexes and this interest has extended into the chemistry of the analogous indenyl (Ind) and tris(pyrazolyl)borate (Tp) (see Tris(pyrazolyl)borates) complexes. Some of the major developments in this area are outlined in the following sections. 

Cyclopentadienyl (Cp) complexes (see Cyclopentadienyl) are known for almost all the metals of the periodic chart, including technetium. The compounds with transition metals usually possess covalent jt Cp M bonding. The nature of the metal Cp bond is multiple. The <7-bond is formed from the overlap of an empty d orbital of Tc with one of the frUed jt bonding molecular orbital on Cp with good symmetry. Back-donation is usually also present from the filled d orbitals of Tc to one of the empty n molecular orbitals on Cp. These molecules are usually called sandwich compounds (see Sandwich Compound), when there are two Cp ligands bonded to the metal, or half-sandwich complexes (see Half-sandwich Complexes) when only one Cp ligand is present. 

Ln cyclopentadienyl Cp) complexes have been known for over half a century... 

It will be important to gain more knowledge of the in vivo metabolism of ruthenium(II) arene complexes of potential interest as drugs. Little is currently known, but some studies on metal cyclopentadienyl (Cp) complexes have been reported. For ferrocene, [(Cp)2Fe], a coordinated Cp ring is hydroxylated in the liver via the P-450 system (Fig. 2.11) [78]. 

Figure 4.63. Molecular structures of commonly used CVD precursor classes. Shown are (a) metal p-diketonate (acetylacetonate, acac) complex to grow a metal oxide film (H2 as the coreactant gas yields a metal film) (b) a heteroleptic (more than one type of ligand bound to the metal) p-diketonate complex to yield a Cu film the ancillary ligand helps prevent oligomerization, enhancing volatility (c) various types of complexes to deposit metalhc, oxide, nitride, or oxynitride films (depending on coreactant gas(es) used - respective ligands are p-ketoiminato, P-diketiminato, amidinato, and guanidinato (d) a metal azolato complex commonly used to deposit lanthanide metal films metal cyclopentadienyl (cp) complexes, (e), and dialkylamido complexes, (f), are often used to deposit a variety of metallic or compound thin films.

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