Metalation ferrocene

Water-soluble sensors for transition metals ferrocene polyazamacrocycles 28 Reducible cation sensors 35... 

WATER-SOLUBLE SENSORS FOR TRANSITION METALS FERROCENE POLYAZAMACROCYCLES... 

Carbonation and subsequent hydrolysis of either lithiated or sodiated metallocenes lead to the corresponding carboxylic acids. Ferrocenecarboxylic acid and ferrocene-1,1 -dicarboxylic acid are readily produced in this manner and can be conveniently separated by extraction of the former with ethyl ether or benzene. The reaction of metalated ferrocenes with various chlorosilanes has led to a variety of triaryl- or trialkvlsilylferrocenes (3, 28, 90). 

Metalated ferrocenes have served as valuable intermediates for the synthesis of a number of other derivatives. Treatment of lithiated ferrocenes with tributyl borate followed by hydrolysis leads to ferroceneboronic acid (XXXIII) as well as the diboronic acid (73). Ferroceneboronic acid, like benzeneboronic acid, is readily cleaved by cupric bromide or cupric chloride to form the corresponding halo derivatives (XXXIV). Ferrocene-l,l -diboronic acid reacts in the same manner, and either one or two carbon-boron bonds can be cleaved. Further reactions of this type have led to a variety of mixed dihaloferrocenes (73, 75). 

Metalated ferrocenes also serve as convenient precursors to ferrocenylboranes. Lithiated ferrocenes have been ntilized for the preparation of ferrocenylboronates FcB(OR)2 and l,T-fc(B(OR)2)2 and are especially suitable in the presence of ort/ o-directing donor-substituents. The borylation of disilylated ferrocenes with excess BCI3 on the other hand was reported to yield varying amounts of 1,3-diborylated prodnct (82 M = Fe, X = Cl) in addition to the l,F-diborylated species (83 M = Fe, X = Cl). In contrast, when 1,F-distannylated ferrocenes were treated with equimolar amounts of boron halides, l-stannyl-2-borylferrocenes (86) were formed as the major product rather than the expected... 

A number of other metalated ferrocene derivatives containing a M-C bond (M = B, Cu, Si, P, Ge, As, Sn) can be prepared from (322) and (323)." Lithiation of alkyl-substituted ferrocenes occurs both homo- and heteroannularly, while the lithiation of A,A-dimethylaminomethylferrocene (289, R = H) is directed to the 2-position by chelation with the nitrogen lone pair see Lone Pair), to give... 

Although nBuLi metallates ferrocene to give a mixture of both Fc-Li and fcLi2 under almost any conditions (see above), the isomeric tBuLi gives exclusively and cleanly monolithio-ferrocene, Fc-Li, in Et20 solution [38, 282] (see Appendix). 

There have been substantial developments in the chemistry of the stannnylmetallocenes, particularly the stannylferrocenes, in recent years. These can be prepared by transmetal-lation of the metallated ferrocenes (Scheme 9-5 and equation 9-54),102 or of a lithium stannylcyclopentadiene with FeCl2 (Scheme 9-6).127 The products can be symbolised by the shorthand I cSnn, where the subscripts x and y indicate the numbers of stannyl groups in the separate cyclopentadienyl rings. The stannylruthenocenes can be prepared in a similar way.128... 

The cyclopentadienyl ligand, generally abbreviated as "Cp," is a common anionic ancillary ligand in organometallic chemistry. Complexes of this ligand or its substituted derivatives are known for all transition metals and for most /-block metals. - Ferrocene is the classic cyclopentadienyl compound, and the identification of the structure of this species by Woodward, Wilkinson, and co-workers, after initial misassignment, is legendary7 °... 

Actually, cyclometalation of a benzene ring proceeds [30]. The ferrocene ring has a high basicity because of the coordination of iron atom, hence, in the case of simple metalation, ferrocene reacts more easily than benzene [85]. But it is thought that the strain of the five-membered ring attached to benzene is less than that of ferrocene since cyclometalation of benzene actually proceeds [86]. 

Metallated ferrocenes are of great importance as intermediates. Metallation may be achieved by reaction of ferrocene with butyl lithium, amyl sodium or phenyl sodium [317, 345, 346, 347], Mixtures of mono- and di-metallated products are frequently obtained unless particularcare is paid... 

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... 

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