mL). Na2C03 was added until the solution pH was about 5. Ti02 (anatase, MCB, 3.0 g) was added. While being stirred in a quartz tube, the mixture was irradiated with a 500-W Xenon lamp for 10 h. The mixture was centrifuged to isolate the solid, which was then washed 4 times with 25 mL of H20. The platinized (grey) Ti02 was dried in an oven (132 °C) overnight. Lower loading levels were attained by a modification of the same procedure.Photolysis Procedure. Ti02 (5 mg) was added to a solution of diacid (0.01 M) in 50 mL of aqueous HN03 (pH = 1), which was agitated in an ultrasonic bath for 15 min to form a suspension. Magnetically stirred reaction mixtures in Pyrex tubes were irradiated in a Rayonet photochemical reactor (temperature ca. 52
Addition to phospholes of gaseous HCI at -90 "C or of an excess of trifluoromethanesulphonic acid at -70 "C, results in P-protonation. The triflate solutions are stable up to room temperature, but the 1 Hphospholium chlorides form P V adducts at -70 "C, which rapidly rearrange by a [1,5]sigmatropic Hshift. The observed product is a 1 -chloro-2,5-dihydrophospholium chloride. Addition of a chloride ion source to the triflates produces the same result. Unprotonated 3,4-dimethyl-1 -phenyl phosphole was found to react at a double bond of its 1H-phospholium ion, forming a crystalline 1,3'-biphospholium dimer.Considerable evidence has accumulated recently to support the concept that among phosphole derivatives [ 1,5] sigmatropic shifts of P-substituents to a ring a-carbon atom are common. Such rearrangements have been encountered when the phosphorus has co-ordination states of three (H' and phenyl migrations), four (phenyl migration 2), and five (phenyl and alkoxy 4 * 5 migration). Migration appears to be faster for H than for phenyl, with alkoxy slower than either; also Pv derivatives rearrange faster than PIv and PI''. A combination of these two effects suggests that rearrangement should be exceptionally fast when H is a substituent on phosphorus(v), as in a h5-phosphole * This appears to be a new observation for a phosphine salt. Other examples have been encountered in related work and will be reported elsewhere (L. D. Quin and S. E. Belmont).1969, 91, 3308.
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