F acceptors

In solvents of this kind, compounds that are formed with F-donors possess alkaline properties, whereas compounds affiliated with F-acceptors take on acidic properties. For instance, MBrF4 (where M = alkali metal) is alkaline whereas BrF2NbF6 displays the property of an acid. A typical interaction that takes place during the synthesis can be represented as follows ... 

The cyclization of 1,19-dideoxybilene-i-dicarboxylic acid esters has been widely used for the synthesis of porphyrins. In this case, the use of tert-butyl esters which can be hydrolyzed with trifluoroacetic acid prior to the cyclization step is necessary. The cyclization step also requires trifluoroacetic acid and orthoformates. However, attempts to prepare porphyrins with /f-acceptor substituents can give rise to problems with side products and yields. 

Preparation. Its prepn was first carried out by the action of metals as F acceptors on N trifluoride in a flow reactor at 375°, conversion 42—62%, yield 62—71% (Ref 1). It has also been prepd by the passage of N trifluoride thru a fluidized bed of powd C at 400—500°, conversion 38%, yield 77% (Refs 3 3a) or by the oxidn of difluor-amine (Ref 6)... 

An additional geometrical effect can be expected from the fact that the nN—ctcf interaction transfers electronic population into the C—F antibond, thus significantly lengthening and weakening this bond.92 As seen in Table 3.24, the C—F acceptor bond of NH2CH2F is lengthened by more than 0.04 A in the perp — anti transition, which is consistent with this expectation. 

Figure 7 Fluorescence intensity ratio, Ia/Id °f acceptors at 417 nm and donors at 360 nm plotted against the molar fraction of MP-CUA in mixed LB films with (O) PA and ( ) AA. The dotted line shows the calculated dependence.

In combination with F acceptors, yielding fluorocations of xenon, as in the formation of (XeFsXAsFg) and (XeFs)(PtF6) ... 

Both XeF4 and XeF6 can act as F" acceptors as well as F" donors and thus form anionic species in reactions such as... 

Stronger fluoro acids AsF5, SbF5 and BiF5 (A) are sufficiently good F acceptors to cause AgF3 to enter into solution in aHF first as Ag(III)(solv) and finally as Ag v) with liberation of fluorine. 

Not only is the Ag2+ species a stronger F acceptor than (AgF)"+ it is also a more potent oxidizer. This is demonstrated by the quick evolution of IrF6 in the reaction of LiIrF6 with Ag(SbF6>2-... 

Complexes of XeFj with F" acceptors were discovered in three separate laboratories. " The 1 1 complexes with AsFg and BF3 Were formulated on the basis of infrared evidence, by Bartlett, et as XeF, salts. Although the crystal structure determination of [XeFs lPtF "] and its relative... 

The products obtained on reaction of ONF with MFe not only reveal an increase in electron affinity from WFe to PtFs but also demonstrate a marked decrease in F acceptor ability — at least from ReFe to PtFg. Although WFe cannot oxidize NO, it readily adds F ... 

Abstract F acceptors (BFs, AsFs, SbFs, or BiFs) added to solutions of NiFs " salts in anhydrous hydrogen fluoride (aHF) below -65 °C precipitate the tan solid NiFa. This solid, preserved at <-65 °C, is quantitatively converted, by 2 equiv of F donor (XeFs or KF) in aHF, to dissolved NiFe ". Dry NiF4 loses Fa above -60 °C, the decomposition to nearly black NiFj becoming rapid at 0 °C. When the dry NiF4 is prepared from KaNiFe, inclusion of some K leads, on thermolysis at 0 °C, to a pyiochlore form of NiFs (P-NiFs). P-NiFs contains K+ in the open channels, with K NiFs, a R5 0.1, The nearly cubic P-NlFs unit cell is rhombohedral oo — 9.933(3) A, a = 91.01(3)°, 980 h ,... 

The idea was not new however. Court and Dove in 1971 had described both the precipitation, at 20 °C, of MnFa from solutions of KaMuFs in aHF, and a black precipitate, claimed to be Nip3, from a like solution of KaNIFs, using AsFs as the F" acceptor. This black NiFj was described as decomposing to NiF, when the AsF " salt produced along with it was extracted with aHF at 20 °C. In addition they remarked explicity that NiFa was not produced from the KrNiF with AsFs reaction. 

The decomposition of N1F4 in aHF at 0 C proceeds smoothly, in several hours (in the presence of a F" acceptor), to a black solid which has the approximately hexagonally close-packed structure (R-NiFs, Table 2) common to the late transition series element trifluorides ... 

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