Trifluoride anion

The solvent induced temperature dependence of NMR parameters (proton and fiuorine chemical shifts and the two-bond scalar spin coupling across the hydrogen bond, Vff) for dihydrogen trifluoride anion, (FH)2F , in a polar aprotic solvent, CDF3/CDF2CI has been reported and analysed by Golubev et al ... 

Calculations performed on the hypervalent lO-F-2 6) trifluoride anion (7) are consistent with the bonding diagram. This hypervalent species consists of a 3c-4e bond that has a partial negative charge of -0.515 at each terminal fluorine and a partial positive charge of 0.030 at the central fluorine. This charge separation indicates that the formal octet expansion is distributed over the three atoms of the hypervalent bond. 

Many perfluoroaUphatic ethers and tertiary amines have been prepared by electrochemical fluorination (1 6), direct fluorination using elemental fluorine (7—9), or, in a few cases, by fluorination using cobalt trifluoride (10). Examples of lower molecular weight materials are shown in Table 1. In addition to these, there are three commercial classes of perfluoropolyethers prepared by anionic polymerization of hexafluoropropene oxide [428-59-1] (11,12), photooxidation of hexafluoropropene [116-15-4] or tetrafluoroethene [116-14-3] (13,14), or by anionic ring-opening polymeriza tion of tetrafluorooxetane [765-63-9] followed by direct fluorination (15). 

Catalytic curing agents initiate resin homopolymerization, either cationic or anionic, as a consequence of using a Lewis acid or base in the curing process. The Lewis acid catalysts frequently employed are complexes of boron trifluoride with amines or ethers. 

The most important reaction with Lewis acids such as boron trifluoride etherate is polymerization (Scheme 30) (72MI50601). Other Lewis acids have been used SnCL, Bu 2A1C1, Bu sAl, Et2Zn, SO3, PFs, TiCU, AICI3, Pd(II) and Pt(II) salts. Trialkylaluminum, dialkylzinc and other alkyl metal initiators may partially hydrolyze to catalyze the polymerization by an anionic mechanism rather than the cationic one illustrated in Scheme 30. Cyclic dimers and trimers are often products of cationic polymerization reactions, and desulfurization of the monomer may occur. Polymerization of optically active thiiranes yields optically active polymers (75MI50600). 

This last reaction is typical of many in which F3CIO can act as a Lewis base by fluoride ion donation to acceptors such as MF5 (M = P, As, Sb, Bi, V, Nb, Ta, Pt, U), M0F4O, Sip4, BF3, etc. These products are all white, stable, crystalline solids (except the canary yellow PtFe ) and contain the [F2CIO] cation (see Fig. 17.26h) which is isostructural with the isoelectronic F2SO. Chlorine trifluoride oxide can also act as a Lewis acid (fluoride ion acceptor) and is therefore to be considered as amphoteric (p. 225). For example KF, RbF and CsF yield M [F4C10] as white solids whose stabilities increase with increasing size of M+. Vibration spectroscopy establishes the C4 structure of the anion (Fig. 17.29g). 

The boron atom in BF5 can complete its octet if an additional atom or ion with a lone pair of electrons forms a bond by providing both electrons. A bond in which both electrons come from one of the atoms is called a coordinate covalent bond. For example, the tetrafluoroborate anion, BF4 (31), forms when boron trifluoride is passed over a meral fluoride. In this anion, the formation of a coordinate covalent bond with a fluoride ion gives the B atom an octet. Another example of a coordinate covalent bond is that formed when boron trifluoride reacts with ammonia ... 

C21-0093. Some pure liquid interhalogen compounds are good electrical conductors, indicating that they contain cations and anions. Show a Lewis acid-base reaction between two bromine trifluoride molecules that would generate ionic species. 

Homogeneous catalysts are also often used in cationic and anionic polymerization processes. Lewis acid catalysts, such as boron trifluoride and stannic chloride, accept protons from co-... 

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

Use a slanted line to show the cleavage of (a) boron trifluoride-water (BF3-H2O), (b) sodamide, and (c) AIBN in cationic, anionic, and free radical initiations, respectively. 

Similar products were obtained from metallic silver and from barium chloride (Table 1), though the residues- from the fluorides of other electropositive elements did not show a stoichiometric composition. This apparent anomaly may be explained by supposing that, in general, bases containing the (BrF )- anion are less stable than the acids, and that a number of compounds of this type lose bromine trifluoride at room temperature. The potassium, silver and barium compounds are... 

The behaviour of chlorine irifluoride differs sharply from that of bromine trifluoride for, when it is added to potassium fluoride, the latter may be recovered quantitatively by evaporation in vacuum at room temperature. The same is true of other metallic fluorides and it appears that the (C1F4) anion is inherently unstable. There is some indication that chlorine trifluoride may form acids with the fluorides of some of the non-metallic elements, though this point has not cis yet been fully investigated. No direct evidence is yet available as to whether other halogen fluorides can give rise to acids and bases, though this is perhaps less probable for compounds such as CIF, BrFj and IF7. 

IR spectra, 22 177-179 Raman spectra, 22 178, 179 triazole and triazolate complexes, 32 180 trifluoride, structure, 27 90, 91, 92, 95, 97 trifluorophosphine complexes cyclopentadienyl, 29 103 hexakis anion, 29 53-54 [Ni4(0CH3)4(acac)4(CH3OH4)l, 43 323 Nitramide, reaction mechanisms, 22 138, 139 acid catalysis, 22 139... 

Complexes, such as 1, also readily react with anions of amines the effect of added Lewis acids was investigated boron trifluoride-diethyl ether complex exerted little effect upon the reaction, but addition of titanium(IV) chloride or tin(lV) chloride inhibited the Michael addition45. 

Such a bond, in which the donor molecule (or anion) provides both bonding electrons and the acceptor cation provides the empty orbital, is called a coordinate or dative bond. The resulting aggregation is called a complex. Actually, any molecule with an empty orbital in its valence shell, such as the gas boron trifluoride, can in principle act as an electron pair acceptor, and indeed BF3 reacts with ammonia (which has a lone pair, NH3) to form a complex H3N ->BF3. Our concern here, however, is with metal cations, and these usually form complexes with from 2 to 12 donor molecules at once, depending on the sizes and electronic structures of the cation and donor molecules. The bound donor molecules are called ligands (from the Latin ligare, to bind), and the acceptor and donor species may be regarded as Lewis acids and Lewis bases, respectively. 

Cationic mechanisms are much more characteristic of the polymerization of oxygen heterocycles, both ethers and acetals. A wide variety of catalysts has been used, including protonic acids, such Lewis acids as boron trifluoride, phosphorus pentafluoride, stannic chloride, antimony pentachloride, titanium tetrachloride, zinc chloride, and ferric chloride, and salts of carbocations or tri-alkyloxonium ions having anions derived from Lewis acids. Some complex, coordination catalysts that appear to operate by a mechanism... 

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