Synthesis, Structure, and Reactivity of Titanium Phosphinimide Thiolate Complexes

Abstract

A series of titanium−phosphinimide thiolate complexes were prepared employing either thiolate for chloride metathesis or protonolysis of metal−carbon bonds by thiols. In these ways the following species were obtained: CpTi(NPR‘3)(SR)2 (R‘ = i-Pr, R = CH2Ph 3; Ph 4, t-Bu 5, (SR)2 = S2(CH2)2 6, S2(CH2)3 7, S2(CH2)2C6H4 8; R‘ = t-Bu, R = CH2Ph 9; Ph 10, t-Bu 11); Cp(t-Bu3PN)TiMe(SPh) 12; and (t-Bu3PN)2Ti(SR)2 (R = CH2Ph 14; Ph 15, t-Bu 16). Reactions of (t-Bu3PN)2TiMe2 with 1 equiv of HSCH2Ph gave a cyclometalated species 17, (t-Bu3PN)2Ti(η2-SCHPh). The analogous reaction of 1 equiv of phenylthiol generated the species (t-Bu3PN)2Ti(Me)(SPh) 18. While 17 and 18 could not be isolated free of 14 and 15, respectively, the analogous reaction of tert-butylthiol afforded (t-Bu3PN)2Ti(Me)(St-Bu) 19 cleanly. Attempts to effect sulfur insertion into Ti−Me bonds were undertaken via the reaction of (t-Bu3PN)2TiMe2 with S8 but gave instead the species (t-Bu3PN)2Ti(η2-S5) 20. The reactivity of the thiolate derivatives, 3−5 with excess AlMe3, was examined. Spectroscopic and crystallographic studies revealed the formation of (CpTi(μ-SR)(μ-NPi-Pr3)(C)(AlMe2)2(μ-SR)AlMe (R = CH2Ph 21, Ph 22, t-Bu 23). Analogous reactions of 7 and 8 with AlMe3 afforded [Cp(i-Pr3PN)Ti(SRS)]·(AlMe3)3 (R = (CH2)3 24, ((CH2)2(C6H4)) 25). The mechanistic implications of the observed multiple C−H bond activation are considered. Crystallographic studies of 4, 6, 7, 14, 16, and 20−23 are reported.