Pentafluorophenyl group

Triaryl-substituted imines are converted to the corresponding nitrones by peroxyacetic add [87] (equation 79) substitution of one pentafluorophenyl group by a phenyl group at the carbon atom reduces the yield to ca. 20% [[Pg.349]

Tnmethylpentafluorophenylsilane reacts with ketones in the presence of cyamde ion to form the silyl eiher denved from the alkoxide created by the addition of the pentafluorophenyl amon to the carbonyl carbon [89] The nucleofugal character of the pentafluorophenyl group is significantly greater than that of the added cyamde ion so that the addihon proceeds under nearly neutral condmons (equation 73)... 

The X-ray structure of meso-hexa(pentahuorophenyl)hexaphyrin 80 found to be an expanded frans-porphyrin was reported recently by Aveiro s group. In the NMR, the two NH protons appear at -1.98 ppm and the four inside pyrrole CH protons as a singlet at -2.43 ppm, while in the NMR, just two kinds of pentafluorophenyl groups were observed in a 2 1 ratio (99CC385). These results indicate that in solution compound 80 exists in a rapid equilibrium between 80a and 80b. 

Using the electron-withdrawing pentafluorophenyl group, two types of 5-coordinate compound have been made (Figure 2.108). 

Pentafluorophenylcopper is representative of a series of fluori-nated organocopper compounds that are highly soluble in organic solvents, more thermally stable than their hydrocarbon analogs, and useful as synthetic intermediates. " Pentafluorophenylcopper has been used to introduce the pentafluorophenyl groups and as a reagent for an improved Ullman diphenyl ether synthesis. It is... 

The pentafluorophenyl group imparts greater crystallinity to the complexes and as a result many complexes have been studied by X-ray crystallography. Although vith other metal centers C Fs-CaFs or CfiFs-CfiHs n-n stacking interactions are observed [21, 22], there are not many examples in gold chemistry and they have been sho vn very recently [23]. 

The trinudear complex [Au3(p-triphos)(QF5)3] [97] in dichloromethane shows an absorption around 270 nm and in the solid state at room temperature the complex does not emit, even using an excitation frequency below 300 nm. At lower temperature (77 K) the complex emits with a maximum at 450 nm. Thus luminescence properties can be dramatically influenced by the pentafluorophenyl group which indicates its important contribution to the energy levels involved in the electronic transitions. 

The trinuclear complex [(Au2S2CNR2)] (PPh2)3CH Au(C6F5)] [102] (Figure 3.10) has an IR spectra that confirms the presence of the pentafluorophenyl group bonded to the Au(I) atom. The P H NMR spectrum shows a doublet at 43.6 ppm and a triplet at 41.2 ppm while the F H NMR spectrum shows the typical pattern for the pentafluorophenyl group bonded to the Au(I) atom. 

Figure 3.16 Tetranuclear complex with inequivalent pentafluorophenyl groups.

When [AuTl(C6F5)2]n reacts with DMSO the complex [Tl2 Au(C6F5)2 2 lt-DMSO 3]n [126] is obtained. The crystal structure of this complex shows unsupported Au - Tl interactions that range from 3.2225(6) to 3.5182(8) A but there are no Tl- - - Tl interactions. There are Au- - - Au interactions of3.733 A and the gold centers are almost linearly coordinated to two pentafluorophenyl groups. The complex is strongly luminescent both at room temperature (emits at 440 nm (exc.390 nm)) and at 77 K (emits at 460 nm (exc. 360 nm)). 

Vicente, J., Bermudez, M.D., Chicote, M.T. and Sanchez-Santano, M.J. (1989) Attempts to prepare mixed diarylgold(III) complexes containing a pentafluorophenyl group. Synthesis of [2- (dimethylamino) methyl phenyl-C 1N)-(pentafluorophenyl)gold(III) complexes. Journal of Organometallic Chemistry, 371 (1), 129-135. 

REAGENTS FOR THE INTRODUCTION OF THE PENTAFLUOROPHENYL GROUP INTO ORGANIC COMPOUNDS... 

The Pentafluorophenyl Group. Fluorine NMR chemical shifts for ortho, meta, and para fluorines can vary considerably (see Chapter 6 for more complete details). Scheme 3.59 provides data for one example, that of pentafluorotoluene. 

The pentafluorophenyl-group has an electronegativity value which has been estimated as being between that of chlorine and bromine so- 2). As would be expected, 3-pentafluorophenyltrifluorobenzyne (9) reacts with benzene to form the 1,4-cycloadduct in good yield 63>. 

The oxime nitrogen can also participate in cycloamination reactions to give pyrroles. Thus, treatment of oxime esters such as 185 with Pd(Ph3P)4 readily affords 186 [129]. The pentafluorophenyl group is necessary for good results otherwise a Beckmann rearrangement can unfavorably enter the picture. The oxime stereochemistry makes no difference on the outcome of the reaction. In addition to 186, pyrroles 187 and 188 were also prepared in this study (among others) [129]. 

An entirely different situation is found in alkynyl halides. Here only examples in which the rearrangement is supported by carbonyl groups [106, 164] or electron-withdrawing pentafluorophenyl groups [165] are known. As one example, the selective reaction of the alkynyl bromide next to the carbonyl group, in the presence of a second alkynyl bromide with a propargylic C-O sigma bond, is shown (88 —> 89) [164] (Scheme 1.38). 

WA Sheppard. Pentafluorophenyl group. Electronic effect as a substituent. J Am Chem Soc 92, 5419, 1970. 

Carbonic Anhydric Hydrolase II / =17nM Figure 3.5 C—F 0=C interactions of fluorophenyl and pentafluorophenyl group. ... 

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