Imido and Organometallic-Amido Titanium(IV) Complexes of a Chelating Phenanthrenediamide Ligand

New titanium(IV) complexes of the chelating ligand N,N‘-bis(3,5-dimethylphenyl)-phenanthrene-9,10-diamide (pada2-) are described. Metalation of padaH2 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 1 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 tBuNH2 afforded the new titanium imido complex (pada)Ti(NtBu)(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)(μ-NtBu)]2 (8).