Imido and organometallic-amido titanium(IV) complexes of a chelating phenanthrenediamide ligand

摘要

New titanium(IV) complexes of the chelating ligand N,N'-bis(3,5-dimethylphenyl)-phenanthrene-9,10-diamide (pada(2-)) are described. Metalation of padaH(2), with TiCl4 in the presence of base afforded the six-coordinate pyridine adduct (pada)TiCl2(py)(2) (1), which was used as a starting point for all further complexes presented in this work. Metathesis of 1 with LiN(SiMe3)(2) afforded the four-coordinate complex (pada)TiCl[N(SiMe3)(2)] (2), free of coordinating pyridine. Further elaboration of 2 with MeLi, PhLi, and PhCH2MgCl provided the mixed alkyl-amido species (pada)TiR[N(SiMe3)(2)] (3a, R = Me; 3b, R = CH2Ph; 3c, R = Ph), which are all stable in the solid state and in solution. Dichloride I reacts directly with 2 equiv of PhCH2MgCl to give the five-coordinate complex (pada)Ti(CH2Ph)(2)(py) (4). The corresponding dimethyl- and diphenyltitanium complexes could not be isolated; however, generation of these species followed by in situ reaction with 'BuNH2 afforded the new titanium imido complex (pada)Ti(=(NBu)-Bu-t)(py)(2) (6). The aryl imido derivative (pada)Ti[=N(2,6-C6H3Me2)](py)(2) (7) was prepared by transimination of 6 with 2,6-dimethylaniline. Imido complex 6 also reacted with benzaldehyde to give the organic metathesis product benzadimine; however, more crowded ketone and imine substrates were unreactive. Prolonged heating of 6 in the absence of reactive substrates led to irreversible dimerization, forming [(pada)Ti(py)(mu-(NBu)-Bu-t)](2) (8).