Naphthalene, 1 ,2,3,4-tetraphenyl

The first reported zirconacydopentadiene was 2,3,4,5-tetraphenyl-l-zirconacyclopenta-diene (la), prepared from two molecules of diphenylacetylene and a low-valent zircono-cene [3]. The low-valent zirconocene spedes was produced by the reaction of Cp2ZrCl2 with sodium/naphthalene (Eq. 2.1). 

There is a difficulty with the mechanism of Scheme 3 in that the fragmentation of a triplet diradical should conserve spin, yet neither triplet Me2Si nor triplet tetraphenyl-naphthalene have been detected. The diradical pathway for the photofragmentation of silanorbornadienes confirms an earlier proposal by Barton and coworkers52. There is always the possibility that diradical intermediates such as the singlet and triplet 13 S and 13 T could function as silylenoids. Thus, the assumption that products from pyrolysis of 7-silanorbornadienes are formed from free silylenes must be treated with caution. 

Figure 10.6. Rate of anionic polymerization of styrene initiated by sodium naphthalene in 3-methyl tetrahydrofuran at 20°C. Left linear variation of rate with (C°)l/2 right inverse linear variation of rate with concentration of Na+ in presence of added sodium tetraphenyl borate. (Data from Schnitt and Schulz [79].)...

The purification of Buckminster fuUerene (Qo) is a typical example of a production rate controlled by the capacity of the mobile phase. In a solvent that gives a retention factor near unity, the solubility is only 800 ppm [69]. In 1-methyl naphthalene, the solubility is close to 5%. To use this solvent, an adsorbent that retains strongly the fuUerenes is needed [70]. A sUica-bonded tetraphenyl-porphyrin gave satisfactory results [70,71]. 

Problem 8.11 Polymerization of styrene with sodium naphthalene initiator was performed at 25°C in tetrahydrofuran (THF) using a static technique [8] that is suitable for monitoring fast reactions. The conversion was determined by monitoring the residual styrene monomer spectrophotometrically during polymerization and the concentration of living ends [M ] was determined spectrophotometrically at the end of the experiment. In independent experimental series, the overall rate constant kp was obtained [cf. Eq. (P8.10.2)] both at different concentrations of initiator (and hence [M ]) without addition of electrolyte and at different concentrations of sodium ions from externally added sodium tetraphenyl borate (NaBPh4) salt and constant concentration of initiator. The data are given below ... 

The least stable of the four isomeric thienothiophenes is thieno[3,4-c] thiophene, which has defied all efforts towards its isolation. Its tetraphenyl derivative (28) has been synthesized and its PE spectrum, obtained by Schweig and coworkers34, is interpreted as verifying that all of these nonclassical condensed thiophenes are aromatic like thiophene itself. The HOMO of 28 is of au symmetry and appears at the very low IE of 6.19 eV. When referenced against its counterpart in naphthalene, it is shown to be missing stabilization from the n orbitals, which is the explanation for its high reactivity. 

A hydroxymethyl group acts as a removable directing group, in a manner similar to that of the carboxyl group in Schemes 25.8 to 25.12, to induce homologation. Under rhodium catalysis, triphenylmethanol (20) couples with 2c in the presence of [RhCl(cod)]2, l,2,3,4-tetraphenyl-l,3-cyclopentadiene (21), and Cu(0Ac)2-H20 as catalyst, ligand, and oxidant, respectively, accompanied by liberation of benzophe-none to produce naphthalene 5b quantitatively (Scheme 25.13) [16]. 

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