Organometallic and related imidotitanium compounds containing a pendant arm functionalised benzamidinate ligand

Chloride ligand substitution reactions of tert-butyl- and arylimido-titanium complexes supported by the pendant arm functionalised N-trimethylsilyl benzamidinate ligand Me3SiNC(Ph)NCH2CH2CH2NMe2 are described. Reaction of previously-described [Ti(NtBu){Me3SiNC(Ph)NCH2CH2CH2NMe2}Cl] (1) with PhLi afforded thermally sensitive [Ti(NtBu){Me3SiNC(Ph)NCH2CH2CH2NMe2}Ph] (2). The corresponding reaction of 1 with MeLi afforded [Ti(NtBu){Me3SiNC(Ph)NCH2CH2CH2NMe2}Me] (3) detected by 1H-NMR spectroscopy but this compound could not be isolated. Reaction of 1 with LiCH2SiMe3 gave a complex mixture, but with LiN(SiMe3)2 and LiO-2,6-C6H3Me2 the compounds [Ti(NtBu){Me3SiNC(Ph)NCH2CH2CH2NMe2}X] (X=N(SiMe3)2 (4) or O-2,6-C6H3Me2 (5)) were isolated. The X-ray structure of 5 was determined. Reaction of the homologous compound [Ti(NtBu){Me3SiNC(Ph)NCH2CH2NMe2}Cl] (6) (containing a 2-carbon atom chain in the pendant arm) with MeLi or PhLi were unsuccessful although the aryloxide compound [Ti(NtBu){Me3SiNC(Ph)NCH2CH2NMe2}(O-2,6-C6H3Me2)] (7) could be isolated from the reaction of 6 with LiO-2,6-C6H3Me2. Reaction of the 3-carbon pendant arm arylimido compound [Ti(N-2,6-C6H3Me2){Me3SiNC(Ph)NCH2CH2CH2NMe2}Cl] (8) with MeLi afforded thermally sensitive [Ti(N-2,6-C6H3Me2){Me3SiNC(Ph)NCH2CH2CH2NMe2}Me] (9), and although the analogous phenyl homologue was elusive, the aryloxide derivative [Ti(N-2,6-C6H3Me2){Me3SiNC(Ph)NCH2CH2CH2NMe2}(O-2,6-C6H3Me2)] (10) was successfully isolated and structurally characterised. Comparison of the X-ray structures of 5 and 10 show unexpectedly large differences between the TiNR and TiOAr bond lengths in the two compounds.