Electron-impact induced fragmentation of some hetero- cyclic-tin compounds

The electron impact induced fragmentation of a series of heterocyclic tin compounds: 10,10-dimethyl- and 10,10-diethylphenoxastannim, the corresponding dimethyl- and diethyltin twelve membered ring heterocycles. 10-10- dimethylphenothiastannin, 10,10-dimethylphenothiastannin 5,5-dioxide, 5,5-dimethyl -5,10-dihydrodibenzo [b,e]stannin and 10,10′ -spirobiphenoxastannin, has been investigated. For the twelve membered ring compounds the results strongly support the structures given by Meinema and Noltes [2]. Primary fragmentation occurs by loss of an alkyl group, in accordance with the preferred tervalency of the tin ion. Further fragmentation pathways were established in each case by defocused metastable measurements and exact mass measurements. Loss of Sn-containing fragments is more common than in Sn- tetraalkyls because of charge stabilisation on the aromatic system.Large differences were observed in molecular ion intensities of the various compounds investigated. Their intensities could be correlated with ionization potentials of the aromatic substituent. A theory attributing this to charge residence in put forward.