C-H AND C-S BOND-CLEAVAGE IN CYCLOPENTADIENYLTITANIUM PHENOXIDE THIOLATE COMPLEXES

The thiolate complexes CpTi(OC6H3-2,6-i-Pr-2)(SR)Cl (R = Et, 1; t-Bu, 2; CH2Ph, 3; Ph, 4) were prepared. Attempts to methylate 1-4 and thus obtain the potentially reactive alkyltitanium thiolate derivatives wer e unsuccessful. Thiolation of CpTi(OC6H3-2,6-i-Pr-2)-(Me)Cl (5) with 1 ,1-dimethylethanethiol in the presence of base afforded the species Cp Ti-(OC6H3-2,6-i-Pr-2)(Me)(SCMe3) (6). The analogous species CpTi(OC6H3 -2,6-i-Pr-2)(Me)(SCH2-Me) (7) is unstable, liberating methane and yiel ding the dimeric product of C-H bond activation, [CpTi(OC6H3-2,6-i-Pr- 2)(mu-SCHMe)](2) (8). In a related thermolysis of CpTi(OC6H3-2,6-i-Pr- 2)(SBn)(2) (9), the dimer species [CpTi(mu-S)(OC6H3-2,6-i-Pr-2)](2) (1 0) and (PhCH2)(2)S are obtained. In contrast, thermolysis of the close ly related species CpTi(OC6H3-2,6-i-Pr-2)-((SCH2)(2)C6H4) (11) and CpT i(OC6H3-2,6-i-Pr-2)(SCH2Me)(2) (12) resulted in no reaction, suggestin g a radical process is operative in the formation of 10. Reduction of 2 with LiPCy2 gave (PCy2)(2) and the S-C bond cleavage product [CpTi(O C6H3-2,6-i-Pr-2)(mu(3)-S)](3)TiCP (13). These pathways of C-H and C-S bond activation are discussed and the implications considered.