Metallocene carboxylates

Falk and Schlogl 42> as late as 1968 established the absolute configuration of compound 13a as (+) —(S)-4-carboxy[2.2]paracyclophane. They did this by kinetic resolution of the racemic carboxylic anhydride with ( —)-a-phenylethylamine this kinetically controlled amidation afforded the dextrorotatory compound (13) in 3.8% optical yield 42C The similar topology of the carboxyl-group environment in 13 and in a-substituted metallocene carboxylic acids (14), configurations con-... 

The cliemistry of the metallocene carboxylic acids is normal and, for example, they form acid chlorides with PCIs [354, 355]. 

Baik and Friesner used an SCRF procedure in conjunction with B3LYP density functional calculations to obtain electrode potentials for groups of aromatic molecules, metallocenes and transition metal complexes in four different solvents 132 the average absolute deviation was about 0.15 volts for a range of values of 3.82 volts. Saracino et al. computed pKa for a series of carboxylic acids with an average absolute deviation of 0.41 for pKa between 1.23 and 5.03.133... 

While metallocenes are usually acetylated with acid halides, acid anhydrides, or carboxylic acids, a number of other acylating agents have been reported. The reaction of ferrocene with various isocyanates and aluminum chlorides leads to N-substituted ferrocenecarboxamides (IX) (89). Use of ruthenocene in place of ferrocene leads to analogous results (88). The preparation of V-phenyl-ferrocenecarboxamide from phenyl isocyanate in this manner has been used as a proof of structure for the product obtained from the Beckmann rearrangement of benzoylferrocene oxime (124). 

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). 

In a slightly different approach, the introduction of a metal complex is also possible as a metallo amino acid. For example, ferrocenyl-alanine (Fer) was prepared as early as 1957 [67]. Also, stereoselective preparations [68-71] and its biological activity were reported [72], and the compound has been inserted into peptide sequences just as a normal amino acid would (see Fig. 7 for an example) [35, 71]. In this case, the metallocene constitutes the side chain. Alternatively, the amino and carboxylic acid function can be on two different Cp rings, yielding, in the simplest possible case, l -aminoferrocene-l-carboxylic acid (Fca, see Fig. 7 for an example). This compound has also been reported in the literature, although it was difficult to obtain in pure form [73,74], It has since been incorporated into oligomers... 

Application of Charge-assisted C H O Hydrogen Bonds in Qrganic-Organometallic Crystal Engineering Carboxyl-Carboxylate Hosts with Cationic Metallocene Guests... 

The chalcogeno esters (E = S, Se, Te) presented in Scheme 5-31 are yellow to red-brown compounds that are air-stable in the solid state [89] the benzoic acid derivatives Fc-S-C(0)Ph [82] and fc(E-C(0)Ph)2 (E = S, Se) [91] had been described earlier. The orange derivatives of the ferrocenyl carboxylic acid contain two or three metallocene units connected by ester links (Fig. 5-12). The corresponding esters of the alcohols Fc-OH and fc(OH)2 (E = O) can be obtained [73] by direct ferrocenoylation using Fc-C(0)Cl. 

Coordination polymerization of hydroxyl, carboxyl and amino monomers can also be effected by the judicious use of protecting groups. For example, amino and hydroxyl monomers have been protected by silyl ethers and aluminate salts for Ziegler Natta and/or metallocene polynrierization and carboxyl monomers have been protected via aluminate salts. Alternatively, organoborane synthons have been used to carry... 

The copolymerization of Tim and Tia with ethylene has been examined using metallocene catalyst systems. Of the two protected carboxylates, Tia appears to be preferred in terms of its incorporation into the copolymer (eq 5). 

Blown film is manufactured from metallocene-catalyzed polypropylene containing a-nucleating agent. The a-nucleating agent is a phosphate ester salt or a carboxylate salt added in quantity of 10 to 5000 ppm. The blown film has improved film forming properties and good optical and mechanical properties. ... 

Aside from the ubiquitous n-alkyl, halide, and alkoxide groups, metallocenes also bear carboxylate, trifluoromethanesulfonate (44), thiolate (45), and other more exotic moieties in addition to the Cp groups. It is commonly believed that these ligands are completely exchanged for alkyl groups originating on the alumi-noxane in the case of MAO activation however, this supposition does not imply that the groups have no effect on olefin polymerization as part of the counterion complex. 

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