Ferrocene hybrids

The rhodium complexes of the ferrocene derivatives 39 have shown useful characteristics for the reduction of itaconates as well as dehydroamino acid derivatives [15, 167-170]. These compounds are hybrids between ferrocene-based ligands and the various other types. The P-chiral compounds, which in some ways are DIPAMP hybrids, showed tolerance for the reduction of N-methyl en-amides to produce N-methyl-a-amino acid derivatives [169-171]. 

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DuPhos. The exception for rhodium-catalyzed reductions are CnrPhos and BPE-4 [168, 264—268]. MalPhos has proven useful for the reductions of yS-acylamino-acrylates [260]. The ferrocene hybrid (FerroTANE) was referred to earlier (see Section 23.4.1) [167, 222]. The PennPhos ligand is useful for the reductions of cyclic enamides and enol acetates both classes of compounds are difficult for DuPhos itself to reduce with high selectivity [269, 270]. 

As summarized in Schemes 12.9 and 12.10, kinetic resolution of propargylic [21] and allylic [22] alcohols work equally well. The DMAP-ferrocene hybrid 21c was also used for kinetic resolution of racemic diols and for the desymmetrization of meso diols [20]. These two applications are discussed in Section 13.3. 

Whereas d8 Ni selects the rectangular di-allylic hyperbonding pattern in (4.121), d6 Fe of ferrocene offers an additional vacant d orbital and hence opens up new geometrical possibilities of an additional cu bond. In concert with the three cu bonds and nominal sd2 (90°) hybridization (Table 4.52), the two Cp ligands are naturally expected to coordinate in r 5 (L2X) fashion to occupy the six octahedrally arrayed coordination sites of the metal. Visualization of this coordination mode is aided by considering the possible patterns of L-type (filled circles 7tcc) and X-type (half-filled circles radical) sites of L2X Cp... 

Zhao, H., et al., Synthesis, characterization, and photophysical properties of covalent-linked ferrocene-porphyrin-single-walled carbon nanotube triad hybrid. Carbon, 2012. 50(13) ... 

Hybrids of ferrocene and fuUerene have been synthesized by treating CjoHMcj... 

Figure 10.14 (a) Schematic representation of hybridization between ferrocene-conjugated oligonucleotide immobilized on gold electrode and its complementary strand, (b) Cyclic voltammograms recorded at v — 2(X) V/s and dependence of the anodic peak current on scan rate, normalized versus v1/2. Reprinted with permission from Ref. 76. Copyright 2003 American Chemical Society. 

The intercalation of polycyclic aromatic compounds into duplex DNA structures was used to develop nucleic acid-based electrochemical sensors.66 For example, the bis-ferrocene-tethered naphthalene diimide (16) was used as a redox-active intercalator to probe DNA hybridization.67 The thiolated probe was assembled on a Au electrode, and the formation of the duplex DNA with the complementary analyte nucleic acid was probed by the intercalation of (16) into the double-stranded nucleic acid structure and by following the voltammetric response of the ferrocene units (Fig. 12.17a). The method enabled the analysis of the target DNA with a sensitivity that corresponded to ca. 1 x 10-20mol. 

There are some reports in the literature concerning the cleavage of bonds between silicon and an sp2-hybridized carbon in silylcyclopentadienyl compounds of type 4 (Section II.B). For example, equation 4697 shows hydrolytic fission in the reaction of a tris(trimethylsilyl) substituted ferrocene derivative with aqueous tetrabutylammonium fluoride. 

There is a certain analogy between the aromatic anions of cyclopentadienide (C5H5 ) and boratabenzene (C5H6B ). l-Methylbora-2,5-cyclohexadienehas a more acidic proton connected to the, sp3-hybridized ring carbon atom than cyclopentadi-ene, due to the same tendency of aromatic anion formation [252, 253]. The related 1-phenyl-1,4-dihydroborabenzene affords the lithium salt of 1-phenylborataben-zene on treatment with tert-butyllithium. Like metallic complexes such as ferrocene formed by cyclopentadiene, boratabenzene also forms such sandwich -complexes with iron and cobalt. The iron complex can be acetylated under Friedel-Crafts conditions. 

It was also found that the hybridization kinetics were found to be faster in a moving sample, as compared to a stationary sample [939]. In another report, active acoustic mixing was used to achieve a five-fold faster DNA hybridization rate. Hybridization was detected electrochemically (by AC voltammetry) based on the ferrocene redox chemistry [62],... 

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