The photodecomposition of platinacycloalkanes in solution.: I. 1,3-propanediylplatinum(IV) compounds |
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Authors: | Duncan CL Perkins Richard J Puddephatt Charles FH Tipper |
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Institution: | Donnan Laboratories, The University, Liverpool L69 3BX Great Britain |
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Abstract: | The gaseous products of the photolysis at 25°C of the platinacyclobutane compounds X2H2(N-N)] where X = Cl, Br and N-N = 1,10-phenanthroline, 2,2′-bipyridine, (CH2NMe2)2, (C5H5N)2 in several solvents, in the absence and presence of various additives, have been determined. With solvents of relatively low dielectric constant (e.g. CH2Cl2), over 85 mol % of the hydrocarbon products was propene, the formation of which appears to involve a direct transfer of a hydrogen atom between neighbouring groups in the ring. With solvents of relatively high dielectric constant (MeCN, Me2SO) in the presence of species, e.g. I?, SbPh3, having a high trans effect, cyclopropane is the main volatile product. The effect of added halide ion and of the mixed solvents Me2SO/PhMe and Me2SO/PhSH indicates that ionisation of the platinacyclobutane and the formation of platinum substituted propyl ion-radicals precede the formation of cyclopropane (and the small amounts of ethylene produced).The photolysis of X2H2(MeCN)2] in methyl cyanide solution in the presence of Et3RNX′ (X′ = Cl, R = H; X′ = Br, R = Et) gives appreciable amounts of ethylene in the products (up to 25 mol %). It is suggested that the halide ions add to the platinum to give negatively charged platinacyclobutane species, the photodecomposition of which may give C2H4. |
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