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A study has been made of the reactions of silicon difluoride with some fluorinated and nonfluorinated aromatic compounds at low temperatures. Perfluorobenzene gives the substitution products CeFsSiFa and C6F4-(SiFs)2;Benzene and toluene give a group of compounds of type ArH(SiF2)", where = 2 to 8. The compounds CeHeSigFe and CeHsCHaSisFe are 1,4-cyclohexadiene derivatives with -SiF2-SiF2-SiF2bridges across the 3,6-positions. These reactions of silicon difluoride have been contrasted with those of carbenes.

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The molecules need not have over-all planar symmetry but planarity would probably be retained in the individual boroxine rings. We can visualize the formation of H4B607 as elimination of a H2 molecule in a reaction of H3B303 at a B-H bond with HzB303(0H) at the 0-H bond. Similarly, H4B404 could be formed from H3B303 and HzB(0H) (hydroxyborane) .* Ion currents of HBO+ and HBOH+ are always observable in these experiments but, because these ions are formed by fragmentation from a number of precursors, it is difficult to assess the importance of the molecular contribution of HBO and HzBOH. These species may be important in the kinetics of reaction as precursors to boroxine.The pressure dependences of reactions 1 and 3 show that the equilibrium concentrations of H4B404 and H4B6-0 7 should increase relative to H3B303 as the pressure of H3B303 increases. Relatively high concentrations of H4B404 and H4Be07 should be possible in a static system where the partial pressure of Hz over B-Bz03 mixtures is of the order of 1 atm at temperatures near 1400'K.Mass spectrometric studies of CuFz sublimation from a Knudsen cell have established CuFz(g) as the major vapor species and AH"~~~[sublimation] = 63.9 f 1.0 kcal mole-'. The dissociation energy of CuF(g) is 87 f 9 kcal mole-' (3.8 f 0.4 ev).

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