Synthesis, structure, and sunlight photolysis of benzyl- and tert-butyl-substituted octamethyltitanocene dihydrosulfides

New titanocene dihydrosulfide compounds [(C5Me4CH2Ph)2Ti(SH)2] (6) and [(C5Me4t-Bu)2Ti(SH)2] (7) were obtained by addition of hydrogen sulfide to the corresponding doubly tucked-in titanocenes, and titanocene hydrosulfide compounds [(C5Me4CH2Ph)2TiSH] (8) and [(C5Me4t-Bu)2TiSH] (9) by H2S-induced protonolysis of σ-Ti–C bonds in [(η5-C5Me4CH2Ph)Ti(III)(η5:η1-C5Me4CH2-o-C6H4)] and [(C5Me4t-Bu)Ti(III)(η5:η1-C5Me4CMe2CH2)], respectively. The crystal structures of 6, 8, and 9 and electronic absorption spectra of 6–9 in hexane solution highly resemble those of corresponding [Cp*2Ti(SH)2] (1) and [Cp*2TiSH] (2), however, compounds 6 and 7 strongly differ in their sensitivity to sunlight mutually and with respect to 1. The sunlight photolysis of 6 in toluene proceeded similarly to the process described previously for 1 except that about three times longer exposition (300 h) was required to obtain the cyclopentadienyltitanium sulfide cage cluster [{(C5Me4CH2Ph)Ti}4S6] (10) in 48% yield. In contrast, compound 7 photo-decomposed very efficiently to give compound 9 as the only isolated titanium-containing product in 87% yield. The formation of 10 can be accounted for the redox elimination of the cyclopentadiene followed by elimination of hydrogen sulfide in intramolecular condensation reaction whereas the formation of 9 requires the dissociation of SH radicals. Both the processes were recognized by Rosenthal and Beweries to concur in photodecomposition of [Cp*2Ti(OH)2].