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The electron resonance spectrum of the mono-anion of tricyano-symtriazine, at 25~ and below, reveals the presence, not of two sets of three equivalent nitrogen atoms, but a set of two and another set of four. It is suggested that the radical-ion undergoes a permanent Jahn-Teller distortion to one of three equivalent distorted forms.

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The infrared spectra of some dinitro-complexes of platinum(II), palladium(II), and cobalt(II1) have been examined. The spectra of the transisomers have bands (some of which are split) in the regions around 1415 (v3), 1330 (VJ, and 822 cm.-l (v2). The cis-isomers have somewhat similar spectra with v1 shifted to rather lower frequency and the characteristic addition of a band a t about 1350 cm.-l; also v2, which is a single band in the spectra of the trans-isomers, is sharply split in the spectra of the cis-isomers. Two binuclear complexes having bridging nitro-groups were also examined. Their spectra have bands due to bridging nitro-groups near 1480 and 1200 cm.-l. From these we infer that the nitro-group forms bridges through the nitrogen and one oxygen atom as hitherto assumed, viz., M-N(0)-0-M.The spectra of a number of mononitro-and polynitro-complexes are also recorded. BEATTIE and TYRRELL examined some nitroammine complexes of tervalent cobalt in the infrared region between 4000 and 700 cm.-l using the potassium bromide disc technique; it was concluded that the geometrical isomers of the dinitrotetramminecobalt (111) complex may be distinguished by examination of the spectra in the 1300 and 850 cm.-l regions. Nakamoto et al., have also interpreted the splitting of the cobalt-ammonia stretching frequencies in various nitroammines in a similar manner. that the spectrum of the cis-dinitrotetramminecobalt(II1) cation, [COIII(NO,),(NH~)~]X where X = a singly charged anion, should show more bands than the trans-isomer, owing to the lower symmetry. An extra band was observed for the cis-isomer in the 1350 cm.-l region.The present work was undertaken to ascertain whether there were features in the infrared spectra which could be used to distinguish between cis-and trans-isomers of planar complexes, and if possible to assign absorption bands characteristic of bridging nitro-groups. The variation of NO, stretching frequencies with different electronic effects transmitted through the metal atom was also investigated.Results and Discussion.-The frequencies of the NO, absorption bands of the compounds examined are given in Tables 1 -4 .

Free radicals are produced by the reaction of hydroxyl radicats and amino-radicals with alkenes or halogenated alkenes. in each case the e.s.r. spectra are attributable to radicals formed by primary addition of an OH or NH, fragment to the olefinic double bond. chemical and Polymer Laboratory, Runcorn, Cheshire HAVING shown1 that the addition of *NH, or *OH radicals to ethylene, results, initially, in the formation of a free-radical species X-CH,cH, (X = NH, or OH), we now report an e.s.r. study of the analogous reactions with propene, but-2-ene, butadiene, crotyl alcohol, vinyl fluoride, and vinyl chloride, The addition of *NH, radicals to a range of vinyl compounds has been studied previously by Corvaja et aZ., and by F i ~c h e r . ~ EXPERIMENTAL An aqueous flow system of the type described by Dixon and Norman 4 was used. The e.s.r. spectra were recorded with a Varian V4500-10A e.s.r. spectrometer equipped with