Ferrocenes cyclopentadienyl ring coordination

Ferrocene Figure 2-47) provides a prime ex.ample of multi-haptic bonds, i.e, a situation where the electrons that coordinate the cyclopentadienyl rings with the iron atom arc contained in molecular orbitals delocalised over the iron atom and the 10 carbon atoms of the cyclopentadienyl rings [82. ... 

More contrasting behavior is displayed by the somewhat related molybdenum complex of l-[(dimethylamino)methyl]-2-(diphenylphosphino)ferrocene, (FcCNP)-Mo(CO)4, in which the octahedral geometry around the molybdenum atom is achievd by coordination of one P atom and one N atom of the adjacent substituents attached to a single cyclopentadienyl ring (see the sketch in Fig. 7-10). In CH2CI2, the irreversible oxidation of the molybdenum fragment precedes the reversible oxidation of the ferrocene moiety [40],... 

In the 3,5-dimethylpyrazolylborato complexes, the molybdenum atom possesses octahedral coordination, similar to that of Mo[HB(3,5-Me2C3N2H)3(NO)(I)-(OCHjCHjBr)] [60] or that of Fe(r/ -C5H4S)2Mo(NO) HB(3,5-Me2C3N2H)3, which is illustrated in Fig. 7-14 [59]. The cyclopentadienyl rings of the ferrocene fragment are parallel and eclipsed. 

Figure 7-47 shows the molecular structure of the diphenylfosphinoferrocene-nickel complex [Fe(fy -C5H4PPh2)2]NiCl2 [150]. The nickel atom assumes an essentially tetrahedral coordination. The cyclopentadienyl rings of the ferrocene group are parallel and nearly eclipsed. 

Finally, Fig. 7-62 illustrates the molecular structure of one of the two complexes shown in Scheme 7-40, namely the cyclometallated diplatinum complex [177]. Both platinum atoms have a square planar coordination. The cyclopentadienyl rings of the ferrocene fragment are eclipsed and somewhat tilted (4.9°) from the parallel arrangement. 

Another copper(i) complex possessing tetrahedral coordination is shown in Fig. 7-66 [187]. The central copper(i) ion is coordinated both to one l,l -bis(diphenyl-phosphino)ferrocene molecule (dppf) and one l,l -bis(oxodiphenylphosphoranyl)-ferrocene molecule (odppf). All the cyclopentadienyl rings are planar and mutually staggered (A/C) or half-staggered (B/D). 

The formation of adducts between CDs and organometallic complexes exhibiting simultaneous first- and second-sphere coordination was reported for the first time by Osa in 1985.Data obtained from induced circular dichroism studies on CDs bearing a ferrocene derivative suggest that one of cyclopentadienyl rings of the ferrocene is included within the CD cavity as shown in Figure 14. 

Electrophilic attack on coordinated cyclopentadienyl rings, particularly those in ferrocene, is well established. This process occurs in a similar fashion to electrophilic attack on arenes and was used to establish the binding mode of the Cp ligand in ferrocene (see Equation 3.88). These reactions of the Cp ligand with electrophiles are described in more detail in Chapter 12, which covers electrophilic attack on coordinated ligands. Friedel-Crafts acylation, formylation, aminomethylation, and mercuration are all known. - ... 

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