Metastable and collision-induced fragmentation studies of all C 4H 12Si +· isomers; a systematic study of structure-reactivity relations

Abstract

Metastable ion (MI) and collision-dissociation (CID) mass spectra have been recorded and compared for all nine C 4H 12Si +· isomers. The (Me) 4Si +·, t-BuSiH +· 3, s-BuSiH +· 3, and (Me) 2EtSiH +· isomers have unique MI and CID mass spectra. The MI mass spectra, including the kinetic energy release values, of (Me)(i-Pr)SiH +· 2 and (Me)(n-Pr)SiH +· 2 are identical, which implies isomerization. MI data also suggest that a fraction of the Et 2SiH +· 2 ions rearrange into branched (Me) 2EtSiH +· ions and a fraction of the n-BuSiH +· 3 ions rearrange into branched s-BuSiH +· 3 ions. A comparison with the isomeric C 5H +· 12 pentanes reveals a crucial difference: H 2 loss occurs for n-BuSiH +· 3, i-BuSiH +· 3, s-BuSiH +· 3, (Me)(n-Pr)SiH +· 2, (Me)(i-Pr)SiH +· 2, and Et 2SiH +· 2, but not for any of the C 5H +· 12 isomers. Generation of four- or five-membered silicon containing rings is suggested for H 2 loss from the C 4H 12Si +· silanes.