Fluorenylidene

Peroxybenzoic Acid,- 9-Fluorenylidene Ester. See 9,9, -Bis(Benzoylperoxy)-F luorene in Vol 2, B135-R... 

Dibrom-fluoren wird zu einem Gemisch aus 9,9 -Dibrom-9,9 -bi-fluorenyl und 9,9 -Bi-fluorenyliden umgesetzt5. 

Der. 80, 133f 372-376, 471 ff., 476f., 480f. O-Acetyl-N-fluorenyliden- 378 O-Acyl- 481... 

It has been possible to record the IR and UV spectra of several derivatives of the carbene [75] - tetrachlorocyclopentadienylidene [80], indenylidene [81] and fluorenylidene [82] (Bell and Dunkin, 1985). These carbenes were formed by UV photolysis of the corresponding diazo precursors frozen in inert matrices and have a triplet ground state. The carbenes [80]-[82] react with CO in inert matrices at 30 K, but exhibit a lower reactivity than the carbene [75]. Furthermore, they were stabilized in a pure CO matrix at 12 K, whereas the free carbene [75] could not be detected under these conditions. The different reactivity towards CO between [75] and [80]-[82] may be associated with the different steric shielding of the carbene centres and with the different triplet-singlet gap as well. 

Final resolution of these problems, particularly the complications from multiple matrix sites, came from investigations using spectroscopic methods with higher time resolution, viz. laser flash photolysis. Short laser pulse irradiation of diazofluorene (36) in cold organic glasses produced the corresponding fluorenylidene (37), which could be detected by UV/VIS spectroscopy. Now, in contrast to the results from EPR spectroscopy, single exponential decays of the carbene could be observed in matrices... 

It is not clear why the sp2-hybridized carbon atom of a fluorenylidene germene (entry 3, Table II) is so shielded (8 79.8), unless this chemical shift is from the spectrum of the THF adduct.28 The chemical shift of the silicon atom in the germasilene (entry 4, Table II) and the phosphorus atom in germaphosphenes (entries 6-10, Table II) is deshielded compared to the corresponding silicon analogs. For example, for Mes2M=SiMes2... 

Ge=CR2 (CR2 = fluorenylidene)28). Tetraaryldigermenes and -germasi-lenes are yellow ( max 408-418 nm), germaphosphenes are orange, the germanethione is orange-yellow,21 and the germaneselone is red.22 Table... 

The sulfur-sulfur bond of dimethyl disulfide adds across the double bond of both Mes2Ge=PAr (Ar = 2,4,6-tri-/-butylphenyl)59 and Mes2Ge=CR2 (CR2 = fluorenylidene)51 possibly via a radical mechanism. 

The two-step reduction of tris(9-fluorenylidene)cyclopropane 2731 and of hexakis(tri-methylsilylethynyl)cyclopropane 5226a requires increasingly more negative potentials than in the cases listed in Table 1 this is, of course, a consequence of the presence of less electron-accepting substituents. Nevertheless, dianion 272 has been generated by reduction with sodium or lithium the lithium salt could be kept in THF solution for up to one year at 20 °C without detectable decomposition31. 

The chloro- or fluorostannanes used were of the type RjXSn-CHRa, where R = bis(trimethylsilyl)methyl or 2,4,6-triisopropylphenyl, R2C is the fluorenylidene moiety and X = Cl or F. Compounds of this type are prepared from R 2SnX2 and LiCHR2. 

An important conclusion, independent of the actual magnitude of AGSX, is that the electron donating methoxy-substituents on the fluorenylidene nucleus lower the energy of the singlet state of the carbene more than that... 

The synthesis of 9-diazofluorene 19 is easily accomplished from commercially available 9-fluorenonehydrazone (HgO, Et20 followed by KOH in EtOH yield = 98%) [72], Diazo compounds on photolytic decomposition tend to generate carbenes [73,74], Fluorenylidene, generated by the photolysis of 9-diazofluorene adds to olefins with negligible amounts of hydrogen abstraction [75,76]. Copper and its salts, however, have been shown to lead to... 

In conjunction with the evaluation of ring current effects and NICS values (Nuclei Independent Chemical Shift), calculations of 3H and 13C NMR chemical shifts for a series of fluorenylidene dications were performed.104... 

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