The preparation is described of the trifluoromethoxides of the heavier alkali metals, i.e. MOCF, where M = K, Rb, or Cs. These are stable, crystalline, ionic solids made by the reversible reaction of carbonyl fluoride with the appropriate metal fluoride. No trifluoromethoxides could be prepared from lithium, sodium, barium, or thallium(1) fluorides. Factors affecting the relative stability of such compounds are discussed.Trifluoromethanol, CFBOH, is not known, and is generally assumed to be incapable of existence because of the ease with which compounds having a fluorine atom in a position a to a hydroxyl group would eliminate hydrogen fluoride. Because of this unavailability of the parent alcohol, no metallic trifluoromethoxides have hitherto been reported. We now report the preparation of stable, crystalline trifluoromethoxides of the heavier alkali metals, i.e. MOCF3, where RII = K, Rb, or Cs.A consideration of the possible formation of metallic trifluoromethoxides shows a t once that they are likely to be more ionic in nature than the corresponding methoxides. The completely ionic formulation M+[OCFJd would contain the trifluoromethoxide ion, isoelectronic with the fluoroborate ion, BF4-. The charge in the trifluoromethoxide ion rests formally on the oxygen atom, but it would be shared to some extent by the three fluorine atoms because of their greater electronegativity. The distribution of charge over the whole ion achieved in this way should therefore stabilize it, in a manner not possible in the ionic non-fluorinated methoxides of the alkali metals. The stability of a solid ionic trifluoromethoxide would clearly be influenced by the nature of the cation present, since smaller cations, or those with a high ratio of charge to size, would cause greater polarization of the anion and a correspondingly greater tendency towards decomposition to give a fluoride ion and carbonyl fluoride. In other words, the equilibrium:would be displaced to the left by the presence of large cations. An immediate corollary of this suggestion is that by approaching the equilibrium from the direction of formation rather than decomposition one would have available a possible synthetic route to trifluoromethoxides.
Ionic, fully fluorinated, ethoxides, n-propoxides, isopropoxides, and n-butoxides of the heavier alkali metals may be made by the reaction of the appropriate acyl fluoride, or of hexafluoroacetone, with the metal fluoride. Factors affecting the stability and possible synthetic use of such compounds are discussed, together with n.m.r. (nuclear magnetic resonance) and infrared spectral data.
Diiodopentafluoroethylphosphine and iodobispentafluoroethylphosphine have been prepared. Reaction of these compounds with silver chloride and silver cyanide leads to replacement of the iodide to give chloro and cyano phosphines. Reaction of RPI2 (R = CBF5, C3F7) with mercury gives the cyclic phosphine (PR)4,5. Conversion of (PC2F5)5 into(PC2F5)4 occurs irreversibly a t room temperature on standing for several days and can be followed by n.m.r. No analogous rearrange- ment was found for (PC3F7)5. Both 31P and 19F n.m.r. spectra for the cyclic phosphine are discussed and compared with those for (PCF3)4,5.
Several alkylmagnesium alkoxides have been prepared by alcoholysis of the dialkyls in diethyl ether, and can be obtained free from ether. In benzene, EtMgOPr", Pr'MgOMe, and Pr'MgOEt are oligomers (degrees of association ca. 8). but those alkoxides we have studied in which there is chain-branching a to oxygen are tetramers, (EtMgO'Pr'),, (EtMgOBd),, and (Pr'MgOPr'),.The 3-ethyl-pentan-3-01 derivative, from Et,Mg + Et,COor Et,Mg + Et,COH, crystallises as an ether complex (EtMgOCEt,.Et,O) which loses ether very readily: the tetrahydrofuran adduct is dimeric in benzene (EtMgOCEt,,TH F),.Some alkylmagnesium alkoxides are tetramers in diethyl ether, (EtMgOEt),, (MeMgOBd),, and (EtMgOBut),, but two are dimers, (EtMgOCMeEt,), and (EtMgOCEt,),.Methylmagnesium t-butoxide disproportionates in dilute solution in benzene. Both dimethylmagnesium and ethylmagnesium ethoxide crystallise from diethyl ether at room temperature without solvent of crystal I isat ion.The diethyl ether complex of t-butoxymagnesium bromide crystallises from the solution obtained when acetone is added to methylmagnesium bromide in ether. It is a dimer, (ButOMgBr,Et,O),, both in benzene and in ether and in the crystalline state. Several analogous products have been obtained by other similar reactions, and all those whose molecular weights were measured were also dimeric (solvent given) examples are ( ButOMgBr,THF), (benzene), (Et,CO M g Br,TH F) , (benzene), ( Et,M eCO M g Br.Et,O) , (ether), (Et,MeCO M g I, Et,O) , (ether), ( Me,PrnCOMgl,Et,O), (ether). t-Butoxymagnesium bromide-diethyl ether complex has also been prepared from magnesium bromideand both Mg(OBut),and MeMgOBut. The 'H n.m.r. spectra of several of the compounds described are anomalous in unexplained ways.South Road, Durham ALKYLMAGNESIUM alkoxides have been mentioned in various connections, and are discussed in a review.l Two of them have been found to be trimeric, (EtMgOEt), in ðyl ether,2 and (BunMgOPri), in b e n ~e n e . ~ Recently,* inethylmagnesium 3-methyl-pentyl-3-oxide has been found to have an apparent degree of association of 2-8 in 0 . 1 1 2 M (calculated as monomer) solution in diethyl ether at 40".
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