Imido titanium compounds bearing the 6-dimethylamino-1,4,6-trimethyl-1,4-diazacycloheptane ligand: synthesis, structures, solution dynamics and ethylene polymerisation capability.
Reaction of Me(4)DACH (6-dimethylamino-1,4,6-trimethyl-1,4-diazacycloheptane) with Ti(N(t)Bu)Cl(2)(py)(3) or Ti(N(t)Bu)Cl(2)(NHMe(2))(2) gave Ti(N(t)Bu)(Me(4)DACH)Cl(2) (1) which in CD(2)Cl(2) solution exists as a mixture of trans and cis isomers (defined with respect to the imido ligand and the exocyclic NMe(2) donor of Me(4)DACH). Aryl imido analogues of 1 were prepared from Ti(NAr)Cl(2)(NHMe(2))(2) and Me(4)DACH forming Ti(NAr)(Me(4)DACH)Cl(2) (Ar = 2,6-C(6)H(3)Me(2) (2), 2,6-C(6)H(3)(i)Pr(2) (3), 2-C(6)H(4)(t)Bu (4), 2-C(6)H(4)CF(3) (5)) which also exist as isomers in solution. The activation parameters for the interconversion of trans- and cis-3were measured by VT NMR spectroscopy. The solid state structures of trans-1, 3 and and cis-2 have been determined. In the presence of MAO or dried MAO the compounds 1-5 act as moderatley productive ethylene polymerisation catalysts, with a modest productivity gain found on moving from the 1/MAO to 1/dried MAO catalyst system.
Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, UKOX1 3TA.
Gregory J
GJ
Hayday
Chao
C
Wang
Nicholas H
NH
Rees
Philip
P
Mountford