Ferrocenyl structure

Bell and Hall have incorporated an organometallic unit into a crown by using the ferrocenyl unit as part of the ring or as a third strand. The unit is incorporated either as the 1,1 -diformylferrocene or the corresponding acid. In the former case, the bis-imine is prepared and reduced to give the saturated crown (see structure 24). In the latter case, the acid is converted into its corresponding chloride and thence into the diamide by reaction with a diamine. Diborane reduction affords the saturated amino-crown. Structure 24 could be prepared by either of these methods but the dialdehyde approach was reported to be poor compared to the amide approach which afforded the product in ca. 60% yield . 

Due to the pronounced electron donating character of ferrocene, ot-ferrocenyl carbocations 3 possess a remarkable stability and can therefore be isolated as salts [16]. They can also be described by a fulvene-type resonance structure 3 (Fig. 4) in which the Fe center and the ot-center are significantly shifted toward each other as revealed by crystal stmcture analysis, indicating a bonding interaction [17]. 

The crystal and molecular structure of the 44, 45, and C5-vinylferro-cenyl-thymidine show that the substituted cyclopentadienyl ring is essentially co-planar with the nucleobase (164). DFT calculations indicate that, irrespective of the extent of saturation in the bridging C2-unit in ethynyl-, vinyl- or ethyl-ferrocenyl-C5-thymidine, a similar amount of spin density is transferred to the nucleobase (Fig. 48). The reduction potentials for these compounds are shifted little compared to the parent ferrocenyl derivatives. 

Fig. 48. Calculated structures for one-electron oxidized C5-ferrocenyl-modified dT derivatives, illustrating distribution of spin-density as a function of linkage. Ref. (164).

Macrocycles attached to redox responsive groups such as ferrocene (78) can give selective transition metal ion receptors. The X-ray structure reveals a five-coordinate zinc with distorted square-pyramidal geometry bound to the four macrocycle nitrogens and an iodide. In the solid state the two ferrocenyl groups are positioned on the same side of the ligand with distances to the metal center of 5.347(7) and 6.120(8) A and these distances can be related to the redox behavior.689... 

Platinum complexes [PtCl2(diphosphine)] and [PtCl(SnCl3)(diphosphine)] of the ferrocenyl diphosphine ligands (35a), (35b), and (36) have been synthesized. Complexes [PtCl2(35)] and [PtCl2(36)] have been structurally characterized by XRD. Both the preformed and the in situ catalysts have been used in the hydroformylation of styrene.112... 

Several new palladium(O) complexes of t-butylphosphine ligands, such as those in Figure 4, have been prepared. For example, the palladium(O) complexes of the parent ferrocenyl ligand113 and of a biarylphosphine191 that was present in Figure 3 have been characterized crystallog-raphically. The palladium(O) complex of the pentaphenylferrocenyl ligand has been identified, but its structure has not been reported.112... 

In addition to the well-known luminescent Re(NAN)(GO)3 moieties, the electrochemically active ferrocenyl groups were employed as building blocks for the construction of polynuclear silver(i) alkynyl complexes. Yip reported the synthesis, structural characterization, and electrochemistry of a tetranuclear complex, [Ag3(dppm)3(C=CFc)(OTf)]OTf 96 (Figure 43), with the Ag3(dppm)3 skeletal unit being capped by a ferrocenylethynyl ligand on one side and an OTP anion on the other, all in a /Z3-771-bonding mode.170... 

Cud has been shown to form a 1 1 adduct with (Ph3P)AuC=CFc (Fc = ferrocenyl), which has a dimeric structure with a square (CuCl)2 core unit of which each Gu atom is coordinated side-on to a triple bond of the substrate. A similar 2 2 aggregate is formed with CuBr and (Ph3P)AuC=CAu(PPh3).66... 

Finally, we have constructed a QM/MM model of complex 3 whereby the phenyl phosphine groups are contained in the QM region, while the ferrocenyl and phenyl substituents on the pyrazole is accounted for on a steric basis only (model E). The agreement between the X-ray structure of 3 and model E is remarkable. For example, both the Pd-P distance and the twist of the coordination plane of the Pd center, 0, are virtually identical to those of the X-ray structure. In fact, the selected parameters displayed in Table 2 are generally better than those of the full QM calculation. The good agreement between the calculated and experimental structures is important for the detailed mechanistic study of the hydrosilylation that is presented in later sections of this chapter. 

The Tripos [73] force field was used to perform the molecular mechanics calculations, augmented with parameters developed by Doman et al. [74] for the ferrocenyl ligand. In the QM/MM hybrid AIMD simulations, the electronic structure calculation was performed on a reduced system in which each of the substituents that have been removed from the QM part was replaced by a hydrogen atom, in order to saturate the valence of the QM boundary atoms. 

In support of the electrochemical evidence, the molecular structure of the biferrocenium ion in [( -CsF Fe -CsfLOf -CsfLOFe -CsHs)] [I3] shows that both pairs of cyclopentadienyl rings have an eclipsed conformation, Figure 16. Furthermore, the mean Fe-Cp(Centroid) distance is equivalent in both the ferrocenyl units and equal to 1.68 A. Speculatively, this value is intermediate between the values previously observed for ferrocene and ferrocenium ions, thus supporting charge delocalization between the two centres.27... 

We consider now the bis(ferrocenyl) molecule in which the two ferrocenyl subunits are separated by a methylene group, namely diferro-cenylmethane. The molecular structure of this molecule is known. The two ferrocenyl subunits occupy two positions of the tetrahedral coordination of the bridging methylene carbon atom. In each ferrocenyl group, the cyclopentadienyl rings assume an eclipsed disposition.28... 

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