Phosphine, flash photolysis

The kinetics of the thermally induced homogeneous decomposition of phosphine (PH3) have not yet been studied. The species PH2, PH and P2 are formed on flash photolysis of PH3 and could be identified by their absorption spectra63. There are proposals as to the mechanism of the consecutive process after the photochemical primary step, but nothing is known about the kinetic parameters of these reactions. With arsine and antimony hydride only the heterogeneous decomposition has been studied64,65. 

The flash photolysis of phosphine, according to spectroscopic results, causes the formation of two phosphorus- and two hydrogen-containing radicals, corresponding to the dissociation of phosphine as shown in Eqs. (6) and (7) >. 

Mixtures of phosphine and oxygen, both above and below the explosion limits, subjected to flash photolysis show, in the spectra, the presence of PH-, OH- and PO-radicals as well as the PH2-radical Eiuiing the reaction of atomic oxygen with phosphine visible luminescence up to 3600 A and UV emission were observed, which were attributed to the partial processes ... 

H-CIDNP and ESR techniques. A laser flash photolysis and time-resolved ESR study of the formation of phosphinoyl radicals from benzoyldiphenyl-phosphine oxide and 257 has appeared. The addition of dialkyIphosphoryl radicals to a fullerene system has also been studied. Interest in adducts of phosphine oxides with proton donors, notably phenols and other solvent guests ° has continued. 

Attempts have been made to record the absorption spectra of radicals produced by flash photolysis of several fluorophosphines and tetrafluorobi-phosphine. Well-resolved spectra were not obtained. Irradiation or thermolysis at 300 °C of tetrafluorobiphosphine in the presence of ethylene leads to tetrafluoroethylenediphosphine. Presumably reaction involves homolysis of the P—P bond to give difluorophosphino radicals. Irradiation of biphosphine disulphides and dioxides in the presence of oxygen gives products derived by initial cleavage of the P—P bond. This hypothesis appears to be substantiated by the observation that (17) is formed on decomposition of (16) in... 

Photochemistry of PH 3 and PD3. The vacuum ultraviolet photochemistry of PH3 and PD3 has received relatively little attention. Ground state PH2radicals have been observed in absorption following the flash photolysis of phosphine and a number of high resolution studies of the PH2(- Mi system have been reported A recent study involving H-atom resonance fluorescence has confirmed the primary production of PH2 radicals via reaction (ix)... 

The formation of diphenylphosphino radicals on photolysis of triphenyl-phosphine, diphenylphosphine, and tetraphenylbiphosphine has been verified. In the case of the reactions of the phosphines, the radicals were trapped with t-nitrosobutane and the resultant nitroxyl radical [Ph2PN(0)Bu ] was identified by e.s.r. The nitroxyl radical has a small P splitting constant, demonstrating that there is no extensive delocalization onto the phosphorus atom. The e.s.r. spectrum of diphenylphosphino radicals, generated by photolysis of tetraphenylbiphosphine in benzene at 77 K, has been observed. When methanolic solutions of the biphosphine or triphenylphosphine are flash-photolysed, a transient species having Amax = 330 nm and which decays by first-order kinetics (A 4 x 10 s )... 

In contrast to the situation on flash pyrolysis, methyleneoxophosphoranes generated by thermolysis or photolysis in the presence of protic nucleophiles can be directly trapped to form corresponding derivatives of phosphinic acid (17- 19) however, the possibility of competing insertion of carbenes into the H/X bond of the additives is always present, giving phosphine oxides with X in the a-position (16- 18). Reaction branching at the carbene 16 was first observed on photolysis of 7 in water 13) and prompted detailed investigations on the phosphorylcarbene/ methyleneoxophosphorane rearrangement. 

---