Synthetic and Structural Studies of Titanium Aminotroponiminate Complexes

The synthesis and characterization of a series of Ti(III) and Ti(IV) aminotroponiminate complexes are described. Six-coordinate [TiMe(2)(Me(2)ATI)(2)] and [TiPh(2)(Me(2)ATI)(2)] were synthesized and structurally characterized, where Me(2)ATI is N,N'-dimethylaminotroponiminate. The mono-alkyl complexes [TiClR(Me(2)ATI)(2)], R = Me, CH(2)SiMe(3), were prepared, and treatment of the former, generated in situ, with PhMgCl yielded the alkyl-aryl complex [TiMePh(Me(2)ATI)(2)]. The solid state structures of most of these complexes were determined and reveal slightly distorted, trigonal-prismatic coordination geometries. Attempts to prepare alkyl complexes containing beta-hydrogen atoms resulted instead in the isolation of [Ti(Me(2)ATI)(3)] or [Ti(2)Cl(2)(Me(2)ATI)(4)], depending on the alkyl reagent and stoichiometry. Because of the modest steric requirements of the {Ti(Me(2)ATI)(2)}(2+) fragment, five-coordinate Ti(IV) complexes were only generated with a bulky sigma-2pi donor ligand, [Ti(N-(2,6)-i-Pr(2)C(6)H(3))(Me(2)ATI)(2)] being a specific example. Attempts to prepare the isoelectronic oxo analogue afforded only dimeric [Ti(2)O(2)(Me(2)ATI)(4)]. Comparison of the metrical parameters for these complexes with those in the literature containing aryloxide and benzamidinate ligands indicate that the {Ti(Me(2)ATI)(2)}(2+) fragment is quite electron releasing.