Ferrocene metallation

A complication that does not extend to other aromatics exists in ferrocene metalation. This is heteroannular dimetalation, which gives products that often contaminate the desired 2-metalation product. This phenomenon was investigated in one instance and from metalation of dimethylaminomethylferrocene with excess n-butyllithium, the l,2,l -tri-substituted product shown in Reaction 3 was isolated (10). Considerable amounts of a l,2,l -trisubstituted ferrocene product could also be isolated... 

Hausler and Taylor [7] used 100 A /i-Styragel with toluene as eluent (0.5-1.0mLmin ) to separate metal salts of dialkylbenzene sulphonates in a petroleum-based matrix. A specially-designed nebulizer was used for ICP-AES detection. A mixture of four ferrocenes was clearly separated into four peaks, in the elution order bis(tetrapyrazolylborate) iron, 1, I -diacetylferrocene, acetylferrocene and ferrocene. Metal detection limits were similar to those obtained with aqueous samples. 

In-situ formation of CNTs in alumina matrices produced by spray pyrolysis might be considered an alternative to the CVD method, which involves spraying a slurry of ferrocene (metal catalysts) and alumina nanoparticles in xylene (hydrocarbon source) at 1000"C under Ar atmosphere [31]. However, the technique produced flake-like mixtures, which showed heterogeneous distribution of CNTs in the matrix material in through-thickness direction. The same spray pyrolysis method was used to fabricate C-SiC-carbon nanotube composite flakes [32]. Other ceramic materials including SiC [33], TiN [34], Fe2N [34], and BaTiOs [35] have also been demonstrated as matrices for incorporation of CNTs by the CVD method. 

In a more recent study," ferrocene moieties are bound onto a ruthenium thin-film surface also by olefin metathesis reactions. With a conjugated chemical linker, two pairs of voltammetric waves are observed, suggesting that interfacial intervalence transfer does take place between the ferrocene metal centers. In addition, the potential spacing between the two voltammetric waves increases with increasing ferrocene surface coverage, suggesting enhanced... 

Metallocenes s. Ferrocenes Metals s. a. Transition metals Metal specificity... 

The preparation and structure determination of ferrocene marked the beginning of metallocene chemistry Metallocenes are organometallic compounds that bear cyclo pentadiemde ligands A large number are known even some m which uranium is the metal Metallocenes are not only stucturally interesting but many of them have useful applications as catalysts for industrial processes Zirconium based metallocenes for example are the most widely used catalysts for Ziegler-Natta polymerization of alkenes We 11 have more to say about them m Section 14 15... 

Section 14 14 Transition metal complexes that contain one or more organic ligands offer a rich variety of structural types and reactivity Organic ligands can be bonded to a metal by a ct bond or through its it system Metallocenes are transition metal complexes m which one or more of the ligands is a cyclopentadienyl ring Ferrocene was the first metallocene synthesized Its electrostatic potential map opens this chapter... 

Other types of bonding include donation by Ligand TT-orbitals, as in the classical Zeiss s salt ion [Pt( 7 -CH2=CH2)Cl3] [12275-00-2] and sandwich compounds such as ferrocene. Another type is the delta (5) bond, as in the Re2Clg ion, which consists of two ReCl squares with the Re—Re bonding and echpsed chlorides. The Re—Re 5 bond makes the system quadmply bonded and holds the chlorides in sterically crowded conditions. Numerous other coordination compounds contain two or more metal atoms having metal—metal bonds (11). 

The methods of preparation of ferrocene have been reviewed by Pauson and by Fischer. Ferrocene has been made by the reaction of ferric chloride with cyclopentadienylmagnesium bromide, by the direct thermal reaction of cyclopentadiene with iron metal, by the direct interaction of cyclopentadiene with iron carbonyl, by the reaction of ferrous chloride with cyclopentadiene in the presence of organic bases such as diethyl-amine, by the reaction of ferrous chloride with sodium cyclo-[lentadienide in liquid ammonia, and from cyclopentadiene and... 

Although not so generally applicable for the preparation of dicyclopentadienyl metal compounds as the sodium cyclopenta-dienide method, the amine procedure represents the simplest preparation of ferrocene. The amine procedure can also be employed for dicyclopentadienylnickel (about 80% yield), using nickel bromide obtained by the action of bromine on nickel metal powder and 1,2-dimethoxyethane as the solvent. The method of preparation given here is a modified version of that originally described. ... 

Tlie importance of bis(cyclopeniadienyl)irou (Fe(jj -C5H3)2( in the developmenl of organo-metallic chemistry has already been alluded to (p. 924). Tile compound, which forms orange crystals, mpl74°, has extraordinary thermal stability (>500°) and a remarkable structure which was unique when first established. It also has an extensive aromatic-lype reaction chernisiry which is reflected in its common name ferrocene The molecular structure of ferrocene in the ciysialline slac features two parallel cyclopentadienyl rings at one lime Ihese... 

The most notable chemistry of the biscylopen-tadienyls results from the aromaticity of the cyclopentadienyl rings. This is now far too extensively documented to be described in full but an outline of some of its manifestations is in Fig. 25.14. Ferrocene resists catalytic hydrogenation and does not undergo the typical reactions of conjugated dienes, such as the Diels-Alder reaction. Nor are direct nitration and halogenation possible because of oxidation to the ferricinium ion. However, Friedel-Crafts acylation as well as alkylation and metallation reactions, are readily effected. Indeed, electrophilic substitution of ferrocene occurs with such facility compared to, say, benzene (3 x 10 faster) that some explanation is called for. It has been suggested that. 

Unsubstituted pentazole (1) would be expected to be a strong acid with a highly aromatic anion (11) which could possibly form ferrocene analogs such as M (N5)2, where Misrepresents a divalent metal... 

Chiral ferrocenes have received niucli attenlion as ligands in metal-calalyzed reactions [39], bul tiieir use in copper cliemislry has been very limited [40, 41]. Hie ferrocene moiety offers die possibility of utilizing botli central and planar cliirality in die ligand. By analogy witli tlie copper arenetiiiolales described above, ferrocenyl copper complex 33 iSclieme 8.20) is extremely inleresling. 

Harrowfield et al. [37-39] have described the structures of several dimethyl sulfoxide adducts of homo bimetallic complexes of rare earth metal cations with p-/e rt-butyl calix[8]arene and i /i-ferrocene derivatives of bridged calix[4]arenes. Ludwing et al. [40] described the solvent extraction behavior of three calixarene-type cyclophanes toward trivalent lanthanides La (Ln = La, Nd, Eu, Er, and Yb). By using p-tert-huty ca-lix[6Jarene hexacarboxylic acid, the lanthanides were extracted from the aqueous phase at pH 2-3.5. The ex-tractability is Nb, Eu > La > Er > Yb. 

---