Conformationally Rigid Diamide Complexes:  Synthesis and Structure of Titanium(IV) Alkyl Derivatives

Titanium complexes bearing a pyridinediamide ligand [2,6-(RNCH2)2NC5H3]2- (R = 2,6-diisopropylphenyl (BDPP); R = 2,6-dimethylphenyl (BDMP)) have been synthesized. The dichloride complexes [2,6-(RNCH2)2NC5H3]TiCl2 are prepared in high yield from {2,6-[(Me3Si)RNCH2]2NC5H3} and TiCl4 via the elimination of 2 equiv of CiSiMe3. Mono(alkyl) and bis(alkyl) complexes are prepared from [2,6-(RNCH2)2NC5H3]TiCl2 and various Grignard reagents. A single-crystal X-ray diffraction study of (BDMP)TiBr(CH2CMe2Ph)·C6H6 (8b·C6H6) revealed a distorted square pyramid structure with the neophenyl group occupying the axial position.