Electron spin resonance studies of organometallic radicals.

A brief account of the principles and experimental techniques of electron spin resonance is given in Chapters 1 and 2. In Chapter 3, the ?-radiolysis of alkyl mercuric halides and dimethyl mercury is discussed. In the spectra of the first group of compounds two radicals were identified, these being R2CHgX and EtHg (or XHg) species. The negative ion MeHgMe- was trapped in irradiated Me2Hg, at 77K. The mechanisms to be found in the solid state radiolysis of trivalent phosphorus compounds are discussed in Chapter 4. The hyperfine couplings for the radicals generated are tabulated and trends in the 31P couplings discussed with respect to the ligand electronegativities. U.v. photolysis of the phosphites (MeO)3P and (MeS)3P is shown to produce two phosphorus centred species, identified as PL2 and MePL3 radicals. Production of radicals of the type H2CSP(SMe)2 occured both on photolysis and ?-irradiation. These radicals did not exhibit the large hyperfine coupling to phosphorus found with H2CCH2PR2 radicals. In Chapter 5 a range of previously unknown PL2 radicals, produced by ?-radiolysis of PL3 compounds, is considered. The 31P hyperfine couplings for these radicals are remarkably constant when compared to a similar group of nitrogen-centred radicals, this being taken to show a very small degree of spin-delocalisation onto the ligands. The radiolytic decomposition of a number of organo- silyl compounds is considered in Chapter 6. The trimethylsilyl radical Me3Si is found to behave normally in a range of solvents, contrary to previously reported results. Chapter 7 covers firstly the matrix isolation of cobalt and manganese carbonyl peroxo-species, and secondly the u.v. photolysis of transition-metal carbonyls, in the presence of t-butyl peroxide. In this latter section the photolysis of MeCpMn(CO)4, Co(CO)3 NO and CpV(CO)4 is discussed. Photolysis of Mn2 (CO)10 MeTHF is not found to give the Mn(CO)5 radical as reported previously.