Ferrocenes substituents

The photochemical reaction of alkoxychromium(0)carbene complexes and ferrocene mono- and disubstituted imines have been reported to form 2-azetidinones having one or two ferrocene moieties in good yields [136]. The chromium(0) carbene complex reacted smoothly with ferrocene imines that allowed to place ferrocene substituents at the N-l, and the C-4, or simultaneously at the N-l and the C-4 positions of the (3-lactam ring, with cis stereoselectivity (Scheme 71). 

When coordinated to a gold centre, the Fc functionalised NHC ligand devised by Horvath et al. shows cytotoxic properties [144]. It is not quite clear what the role of the ferrocene substituent is since the ferrocene is in the para position of the phenyl wingtip group. One might think that such an architecture would render the Fc group sterically irrelevant and electronically somewhat of lesser importance. However, gold(I) phosphane and NHC complexes are known for their antitumour activity [184]. 

Introducing a second Fc substituent into the ligand system is not a principal improvement [158,185]. As we have seen, the effect of the ferrocene substituent is not that substantial. In contrast, symmetrisation can have adverse effects on the catalytic properties since unsymmetrical ligands often show the better results [183]. 

The design concept for the anticancer-active ferrocifen mentioned above is replacement of a phenyl ring by a ferrocene substituent. The very same principle has previously been applied to a number of antimicrobial agents. The first ferrocene derivatives of penicillins and cephalosporins have been synthesized by Edwards and co-workers. Eurther derivatives were later investigated. Unlike the anti-malarials discussed below, there has been no real... 

Cationic initiation and Ziegler-Natta methods have also been employed successfully in order to obtain poly(vinylferrocene) [14]. Due to the electron-donating nature of a ferrocene substituent, it was initially believed that anionic initiators would not be able to induce the polymerization of vinylferrocene. However, in the early 1990s, living anionic polymerization of vinylferrocene in solution was achieved at low temperatures (-70°C to -30°C) in THE using alkyllithium initiators [15]. Block copolymers of poly(vinylferrocene) with poly(methyl methacrylate), PVEc-b-PMMA (2.5) or polystyrene, PVFc-h-PS, as coblocks were also reported (Scheme 2.1) [15]. 

We have prepared and characterized a range of complexes of the new redox active Fctpy ligand, including [Fe(Fctpy)2][PF6]2 (blue), [Cu(Fctpy)2][PF6]2 (red) and [Ru(Fctpy)2][PF6]2- Each of these complexes shows two oxidation processes one is associated with the ferrocene substituent (+0.20, +0.30 and +0.22V respectively) and the other with the other metal centre (Fe, +0.8 IV, Co, -0.18V and Ru, +0.90V). These data have allowed us to define a Hammet redox active terminators into oligomers and into multiple helical systems. 

A. Iraqi and D. F. Pickup. Preparation and characterization of tractable regioregular head-to-tail poly(3-alkylthiophene)s with ferrocene substituents. Polym. Int. 55, 780-783 (2006). 

Addition of thiourea to chalcones containing a ferrocene substituent is usually accomplished by moderate heating of the reactants. The selectivity is low, and chromatographic separation of the products is impaired by their instability. In the presence of sodium ethoxide in ethanol under sonication (Eq. 20), a rapid addition takes place and the adduct crystallizes out of the solution, thus preventing an undesired sonochemical decomposition. 125... 

Apart from the role of bonding with and stabilizing the cyclopentadienyl radicals, the iron atom may also take a direct part in the chemistry of ferrocene substituents, and in the mechanism of substitution. It has been proposed that electrophilic substitutions occur by a general reaction path in which the attacking electrophilic group interacts first with the iron atom to give a ir-diene cationic intermediate ... 

Ferrocene Substituents. Some of the most interesting poly(phosphazenes) that have been prepared from the reactions of the polymer anion 2 with carbonyl compounds are those with ferrocene substituents. 

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