Isomerism in Hexacoordinate Ti(IV) and Zr(IV) Complexes with a Tetradentate ONNO-Schiff Base Ligand

The reactions of [(thf)(2)TiCl4] with sodiated 2,2'-bis[2-hydroxy-3,5-di(tert-butyl)benzylideneamino]-1,1'-biphenyl (1 a) and 2,2'-bis[2-hydroxy-3,5-di(tert-butyl)benzylideneamino]-4,4'-dimethyl-1,1'-biphenyl (1 b) yield the corresponding Ti complexes 2 a and 2 b. Similarly, 1 a reacts with [(thf)(2)ZrCl4] to the corresponding Zr derivative 3. For 2 a, a mixture of cis-beta and trans isomers were observed in solution whereas the Zr congener exclusively forms the cis-alpha form. Quantum chemical calculations verify that these isomers are the preferred molecular structures. The crystal structures of cis-beta isomeric 2 a and cis-alpha isomeric 3 have been determined. Metalation of 1 a with Ti(NMe2)(4) yields 2,2'-bis[(2-oxido-3,5-di(tert-butyl)phenyl)-dimethylaminomethylamino]-1,1'-biphenyl titanium(IV) (4) with a hexadentate ligand.

Automated summary

The reactions of [(thf)(2)TiCl4] with sodiated 2,2'-bis[2-hydroxy-3,5-di(tert-butyl)benzylideneamino]-1,1'-biphenyl (1 a) and 2,2'-bis[2-hydroxy-3,5-di(tert-butyl)benzylideneamino]-4,4'-dimethyl-1,1'-biphenyl (1 b) yield the corresponding Ti complexes 2 a and 2 b. Similarly, 1 a reacts with [(thf)(2)ZrCl4] to the corresponding Zr derivative 3. For 2 a, a mixture of cis-beta and trans isomers were observed in solution whereas the Zr congener exclusively forms the cis-alpha form. Quantum chemical calculations verify that these isomers are the preferred molecular structures. The crystal structures of cis-beta isomeric 2 a and cis-alpha isomeric 3 have been determined. Metalation of 1 a with Ti(NMe2)(4) yields 2,2'-bis[(2-oxido-3,5-di(tert-butyl)phenyl)-dimethylaminomethylamino]-1,1'-biphenyl titanium(IV) (4) with a hexadentate ligand.