Diferrocenyl

Scheme 10.48 Rh-catalysed hydrosilylation of acetophenone with diferrocenyl dichalcogenide ligand.

The electrochemistry of some single-atom bridged ferrocene dimers gives a separation of two le waves. The carbon atoms in CROH and C = 0 can communicate between ferrocene units in 32 and 33 (101). Diferrocenyl sulfide, 34, shows significant AE° values, 0.29-0.33 V, indicating the presence of strong internuclear interactions (102,103). 

Diferrocenyl selone reacts with W(CO)5 THF yielding the selone pentacar-... 

The l,l -diferrocenyl-VT electron donor molecule is structurally similar to diferrocenyltetrathiafulvalene but with the TTF moiety replaced by bis(vinylene-dithio)tetrathiafulvalene (VT) [76]. It has currently not been possible to separate the cis- and trans-isomers. The 1 1 polyiodide complex of l,l -diferrocenyl-VT was obtained through reaction with iodine. EPR and Mossbauer spectra indicate that in this charge transfer salt the VT moiety is oxidized while the ferrocene... 

Over the past decade a number of new covalently bonded TTF/ferrocene adducts have been reported [77, 78]. The crystal structure of the l,l -bis(l,3-dithiole-2-ylidine)-substituted ferrocene derivative has been published [77]. In this complex, ferrocene has essentially been incorporated as a molecular spacer between the two l,3-dithole-2-ylidene rings forming a stretched TTF molecule. This adduct, and its methyl-substituted derivative, have been combined with TCNQ to form charge-transfer complexes with room temperature powder conductivities of 0.2 S cm-1. Similar diferrocenyl complexes have been prepared with bis (dithiolene) metal complexes [79, 80]. 

Ferrocenyl-substituted allenyl cations 28 were generated when 1,3-diferrocenyl-substituted secondary and ferrocenyl-substituted tertiary alcohols 29 were treated with trifluoroacetic acid27. These were rapidly converted into trifluoroacetoxyallylic ions by solvent addition the ions gave ferrocenyl-substituted enones by reaction with water (equation 8). 

Scheme 4.59 Synthesis of chiral allenecarboxylates 233 using chiral diferrocenyl diselenides 231.

Figure 15 qualitatively depicts the cyclic voltammetric responses that one would expect for diferrocenyl molecules according to their charge delocalization. 

Table 8 Formal electrode potentials ( V, vs. SCE), and relative separation (V), for the two one-electron oxidations of a few diferrocenyl molecules...

The 16-Fc derivative displays a similar behaviour (A o, = 0.16 V). Such an electronic situation arises from the presence in each tentacle of the diferrocenyl unit illustrated in Scheme 10, which displays two separated one-electron oxidations (E°f/+ = + 0.45 V . E+/2+ = + 0.63 V), typical of communicating diferrocenes. 

Figure 6 shows the electrochemical behaviour of the diferrocenyl-bis[tris(pyrazolyl)borato]-Fe(II) derivative there schematized, strictly related to the previous complexes.3... 

A further interesting example is offered by the trans- and cis-azo-bridged diferrocenyl couple illustrated in Scheme l.3... 

Asymmetric ferrocenyl ligands bearing different donor atoms connected through a chiral carbon atom have been used by many groups for different enantioselective reactions. Diferrocenyl dichalcogenides 107-109 were synthesized by Uemura et al. and tested in the ATH of acetophenone in the presence of [lr(cod)Cl]2 in PrOH/NaOH to give (Rj-phenylethan-l-ol at moderate conversions and enanh-oselechvities (Scheme 4.49) [95]. 

Catalyhc systems based on the commonly used iridium precursor [ Ir(g-Cl)(cod) 2] and diferrocenyl dihalcogenides of L4 and L5 type were also studied in the asymmetric hydrosilylahon of acetophenone, giving a relahvely high yield of sec-phenetyl alcohol silyl ether (I) and a moderate ee of one stereoisomer [49]. 

Jin et al. 2007). In other words, an intermediate coupling between the mixed-valence centers exists. Therefore, referral of this diferrocenyl compound to the Robin-Day class II category is more appropriate. 

The bridge effect was scrutinized in the range of diferrocenyl derivatives, especially of those that are applicable in catalysis and material science (Atkinson et al. 2004). One-electron oxidation of these derivatives also proceeds easily, reversibly, and gives rise to cation-radicals (ferrocenium ions). In contrast to the cation-radical of ferrocenylacrylonitrile, the hole transfers through conjugated systems were proven for the bis(ferrocenyl)acetylene cation-radical (Masuda and Shimizu 2006), the bis(ferrocenyl) ethylene cation-radical (Delgado-Pena et al. 1983), and the cation-radical of bis(fulvaleneiron) (LeVanda et al. 1976). These structures are presented in Scheme 1.30. 

Lloveras et al. (2005) compared intervalence electron transfer in l,4-diferrocenyl-l,3-butadiene, [Fc—CH=CH—CH=CH—Fc] andin l,4-diferrocenyl-2-aza-l,3-butadiene, [Fc—CH=N— CH=CH—Fc]. Although intervalence electron transfer in [Fc—CH=CH—CH=CH—Fc] and [Fc—CH=CH—Fc] resemble each other, this process in [Fc—CH=N—CH=CH—Fc] is restricted to some degree. As the authors noted, the population of the state with the positive charge located on the iron attached to the 4-position of the 2-aza-l,3-butadiene bridge is dominant, with just a very small population (<0.1%) of the state with the charge on the other iron site (Lloveras et al. 2005). 

Diferrocenyl, Biferrocene or Bicyelopentodieny-lene-bis[cyclopentadtenyl iron]... 

C5H5 C5H5 mw 370.14, Fe 30.18 orn crysts (from ale), mp - darkens at 205° melts with deconipn at 230° readily sol in benz mod sol in petr eth, toluene, dioxane, tetrahydrofuran 8r ale was formed by the decompn of diferrocenyl mercury, (C HjFeC H Hg, in the presence of Pd black (Refs)... 

SCHEME 19. Representative bridged diferrocenyl compounds and their A2 (V) values... 

The interesting zwitterionic compound (39) with the cationic component a butadien-2-yl cation was obtained by reaction of l,4-di(t-butyl)butadiyne with 2 mol of di(r-butyl)aluminium hydride, with the structure being established by X-ray analysis.80 The reactions of the l,2-diferrocenyl-3-(methylthio)cyclopropenylium ion with carbanions derived from active methylene compounds were investigated.81 Products were derived by ring opening of the cyclopropene ring after the initial carbanion addition. The bis(ferrocenylethynyl)phenylmethylium cation (Fc-C=C-)2C+Ph (Fc = ferrocenyl) was prepared 82 This cation proved to be much less stable than its bis-ethenyl analogue (Fc-CH=CH-)2C+Ph. 

Diferrocenyl receptors, synthesis, 12, 471 Differential scanning calorimetry... 

A number of ferrocene-containing 1,3,4-oxadiazoIes have been prepared. The reaction of ferrocenecarboxhydrazide with triethyl orthoformate gave three products, the principal one being 2-ferro-cenyl-l,3,4-oxadiazole (126 R = H). 76 2-Phenyl-5-ferrocenyl-l,3,4-oxadiazole (126 R = CgH5) and 2,5-diferrocenyl-l,3,4-oxadiazole (126 R = ferrocenyl) were prepared from the appropriate 1,2-diacyl-hydrazines.117 A number of other ferrocenyloxadiazoles, including the bis compound 127, were prepared in a similar manner.117 The oxadi-... 

The synthesis of ferrocenyl sugars as exemplified by Fig. 11 and their antimalarial activities have been reported. Whereas the organic parent compound, an ellagitan-nin derivative, trideca-O-methyl-a-pedunculagin, displayed no antimalarial activity, the diferrocenyl glucoside showed inhibitory activity similar to that of quinine against the FCR3 CQ-susceptible strain [99]. 

Ferrocenyl organo tellurium derivatives were prepared from diferrocenyl ditellurium and organic lithium compounds with toluene or tetrahydrofuran as the solvent2. 

Diferrocenyl Tellurium2 A solution of 0.10 g (0.52 mmol) ferrocenyl lithium in 25 ml tetrahydrofuran is mixed with 0.16 g (0.26 mmol) of diferrocenyl ditellurium. The mixture is stirred at 20° for 1 h. The solvent is evaporated and the residue is dissolved in a small volume of dichloromethane. The solution is chromatographed on a silica gel column. Ferrocene and bifcrroccnc arc washed from the column with pentane. Diferrocenyl tellurium and diferrocenyl tellurium are eluted with dichloromethane. The diferrocenyl tellurium compounds are separated on 0.5 mm silica gel layers with pentane/toluene (7 1) as the mobile phase. The orange crystals melt at 164-166° yield 9%. 

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