C−H and C−S Bond Cleavage in Cyclopentadienyltitanium Phenoxide Thiolate Complexes

The thiolate complexes CpTi(OC 6 H 3 -2,6- i- Pr 2 )(SR)Cl (R = Et, 1; t- Bu, 2; CH 2 Ph, 3; Ph, 4 ) were prepared. Attempts to methylate 1 − 4 and thus obtain the potentially reactive alkyltitanium thiolate derivatives were unsuccessful. Thiolation of CpTi(OC 6 H 3 -2,6 -i- Pr 2 )(Me)Cl ( 5 ) with 1,1-dimethylethanethiol in the presence of base afforded the species CpTi(OC 6 H 3 -2,6- i -Pr 2 )(Me)(SCMe 3 ) (6 ). The analogous species CpTi(OC 6 H 3 -2,6 -i- Pr 2 )(Me)(SCH 2 Me) (7 ) is unstable, liberating methane and yielding the dimeric product of C−H bond activation, [CpTi(OC 6 H 3 -2,6- i- Pr 2 )(μ-SCHMe)] 2 (8) . In a related thermolysis of CpTi(OC 6 H 3 -2,6- i- Pr 2 )(SBn) 2 ( 9), the dimer species [CpTi(μ-S)(OC 6 H 3 -2,6- i- Pr 2 )] 2 (10) and (PhCH 2 ) 2 S are obtained. In contrast, thermolysis of the closely related species CpTi(OC 6 H 3 -2,6- i- Pr 2 )((SCH 2 ) 2 C 6 H 4 ) (11) and CpTi(OC 6 H 3 -2,6- i- Pr 2 )(SCH 2 Me) 2 (12) resulted in no reaction, suggesting a radical process is operative in the formation of 10 . Reduction of 2 with LiPCy 2 gave (PCy 2 ) 2 and the S−C bond cleavage product [CpTi(OC 6 H 3 -2,6- i- Pr 2 )(μ 3 -S)] 3 TiCp ( 13) . These pathways of C−H and C−S bond activation are discussed and the implications considered.