189184-16-5Relevant academic research and scientific papers
Ancillary aryloxide ligands in ethylene polymerization catalyst precursors
Firth, Andrea V.,Stewart, Jeffrey C.,Hoskin, Aaron J.,Stephan, Douglas W.
, p. 185 - 193 (2007/10/03)
The compounds CpTiCl2(OC6H3-i-Pr2) (1), CpTiCl(OC6H3-i-Pr2)2 (2), CpTi(R)(OC6H3-i-Pr2)2 (R=t-Bu 3, s-Bu 4, n-Bu 5, Me 6) have been prepared and characterized. Compounds 1 or 2 in the presence of 500 equivalents of methylaluminoxane (MAO) act as catalyst precursors for ethylene polymerization. While the catalysts derived from the monocyclopentadienyl complexes are much less active that the metallocenes, there is a clear enhancement in the activity of about 40% as a result of the inclusion of a second aryloxide ligand. Reactions of 1 with AlMe3 revealed stepwise formation of CpTi(Me)Cl(OC6H3-i-Pr2) 7 and CpTi(Me)2(OC6H3-i-Pr2) 8, while subsequent addition of AlMe3 afforded complete conversion to 8, with formation of the aluminum species [AlMe2(OC6H3-i-Pr2)]n 9. In contrast, the catecholate complex CpTi(O2C6H4)Cl 10 reacts with AlMe3 yielding the paramagnetic species [CpTi(O2(C6H4))·AlClMe2] 2 11. Incorporation of aryloxide ligands in modified metallocenes was readily accomplished with the preparation of Cp2ZrCl(OC6H3-i-Pr2) 12, Cp2ZrCl(OC6H5) 13, Cp2ZrMe(OC6H5) 14 and Cp2TiCl(OC6H3-i-Pr2) 15. In combination with MAO, 12, 14 and 15 effect the polymerization of ethylene with an 11% increase in activity over the parent metallocenedichlorides. The implications of the increased activity are considered. Crystallographic data are reported for 2, 3, 6, 9, 11, 12 and 13.
C-H and C-S bond cleavage in cyclopentadienyltitanium phenoxide thiolate complexes
Firth, Andrea V.,Stephan, Douglas W.
, p. 2183 - 2188 (2018/12/02)
The thiolate complexes CpTi(OC6H3-2,6-i-Pr2)(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 were unsuccessful. Thiolation of CpTi(OC6H3-2,6-i-Pr2)-(Me)Cl (5) with 1,1-dimethylethanethiol in the presence of base afforded the species CpTi-(OC6H3-2,6-i-Pr2)(Me)(SCMe3) (6). The analogous species CpTi(OC6H3-2,6-i-Pr2)(Me)(SCH2-Me) (7) is unstable, liberating methane and yielding the dimeric product of C-H bond activation, [CpTi(OC6H3-2,6-i-Pr2)(μ-SCHMe)]2 (8). In a related thermolysis of CpTi(OC6H3-2,6-i-Pr2)(SBn)2 (9), the dimer species [CpTi(μ-S)(OC6H3-2,6-i-Pr2)]2 (10) and (PhCH2)2S are obtained. In contrast, thermolysis of the closely related species CpTi(OC6H3-2,6-i-Pr2)-((SCH2)2C6H4) (11) and CpTi(OC6H3-2,6-i-Pr2)(SCH2Me)2 (12) resulted in no reaction, suggesting 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(OC6H3-2,6-i-Pr2)(μ3-S)]3TiCp (13). These pathways of C-H and C-S bond activation are discussed and the implications considered.
