Synthesis, structure, and sunlight photolysis of benzyl- and tert-butyl-substituted octamethyltitanocene dihydrosulfides
Abstract
New titanocene dihydrosulfide compounds [(C5Me4CH2Ph)(2)Ti(SH)(2)] (6) and [(C(5)Me(4)t-Bu)(2)Ti(SH)(2)] (7) were obtained by addition of hydrogen sulfide to the corresponding doubly tucked-in titanocenes, and titanocene hydrosulfide compounds [(C5Me4CH2Ph)(2)TiSH] (8) and [(C(5)Me(4)t-Bu)(2)TiSH] (9) by H2S-induced protonolysis of sigma-Ti-C bonds in [(eta(5)-C5Me4CH2Ph)Ti(III)(eta(5):eta(1)-C5Me4CH2-o-C6H4)] and [(C(5)Me(4)t-Bu)Ti(III)(eta(5):eta(1)-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-2*Ti(SH)(2)] (1) and [Cp-2*TiSH] (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}(4)S-6] (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-2*Ti(OH)(2)].