The synthesis, structure and ethene polymerisation catalysis of mono(salicylaldiminato) titanium and zirconium complexes

The silyl ethers 3- Bu-t - 2- ( OSiMe3) C6H3CH = NR ( 2a- e) have been prepared by deprotonation of the known iminophenols ( 1a - e) and treatment with SiClMe3 ( a, R = C6H5; b, R = 2,6- Pr-i 2C6H3; c, R = 2,4,6- Me3C6H2; d, R = 2- C6H5C6H4; e, R = C6F5). 2a - c react with TiCl4 in hydrocarbon solvents to give the binuclear complexes [ Ti {3- Bu-t - 2-( O) C6H3CH = N( R)} Cl( mu - Cl-3) TiCl3] ( 3a - c). The pentafluorophenyl species 2e reacts with TiCl4 to give the known complex Ti {3- Bu-t - 2- ( O) C6H3CH = N( R)} Cl-2(2). The mononuclear five- coordinate complex, Ti {3- Bu-t - 2- ( O) C6H3CH = N( 2,4,6- Me3C6H2)} Cl-3 ( 4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti {3- Bu-t - 2- ( O) C6H3CH = N( R)} Cl-3( THF) ( 5a - e). The reaction with ZrCl4( THF) (2) proceeds similarly to give complexes Zr {3- Bu-t - 2- ( O) C6H3CH = N( R)} Cl-3( THF) ( 6b - e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde titanium complex Ti {3- Bu-t - 2- ( O) C6H3CH = O} Cl-3( THF) ( 7) have been determined. Activation of complexes 5a e and 6b e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending on the imine substituent.