A thermochemical study of dissociative ionization of 4,4-dimethyl-1-thia-4-silacyclohexane and 2,3,3-trimethyl-1-thia-3-silacyclopentane. Decomposition pathways to produce a dimethylsilanethione ion-radical [Me 2SiS]

• Published in: Journal of organometallic chemistry Vol. 288; no. 1; pp. 27 - 33
• Main Authors: Tarasenko, N.A., Volkova, V.V., Zaikin, V.G., Mikaya, A.I., Tishenkov, A.A., Avakyan, V.G., Gusel'nikov, L.E., Voronkov, M.G., Kirpichenko, S.V., Suslova, E.N.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.01.1985; Elsevier Science
• Subjects: Chemistry; Exact sciences and technology; Mass spectrometry; Organic chemistry; Reactivity and mechanisms; Electron impact; Five membered ring; Photoionization; Six membered ring; Sulfur silicon heterocycle; Fragmentation pattern; Mass spectrum; Molecular ions; Dissociative ionization; Organic radical cation
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/0022-328X(85)80102-9

The dissociative ionization of 4,4-dimethyl-1-thia-4-silacyclohexane (I) and 2,3,3-trimethyl-1-thia-3-silacyclopentane(II) has been studied by electron photoionization (PI) mass spectrometric methods. The molecular ion fragmentation is mainly related to the loss of ethylene and results in a [Me 2SiSC 2H 4] +• ( m/z 118) ion-radical ( A). Further loss of ethylene from A produces a dimethylsilanethione [Me 2SiS] +• ( m/z 90) ion-radical ( B). The latter is the most abundant ion in the mass spectra of I and II at 70 eV. The ionization energies (IE) of I (8.22 ± 0.07 eV) and II (8.06 ± 0.03 eV) and the appearance energies (AE) of ion-radicals A and B have been determined. Also, the following heats of formation were calculated (kJ/mol): Δ H f 0(I) = −31.1; Δ H f 0(II) = −65.8; Δ H f 0( M I +•) = 762.0; Δ H f 0( M II +•)= 712.1; Δ H f 0( A) aver = 780.2; Δ H f 0( B) aver = 847.7.