Synthesis, Structure, and Reactivity of Titanium Phosphinimide Thiolate Complexes

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.