New Titanium Complexes with Symmetric or Asymmetric cis-9,10-Dihydrophenanthrenediamide Ligands Formed through Sequential Intramolecular C−C Bond-Forming Reactions

A series of new titanium(IV) complexes with symmetric or asymmetric cis-9,10-dihydrophenanthrenediamide ligands, cis-9,10-PhenH2(NR)2Ti(OiPr)2 [PhenH2 = 9,10-dihydrophenanthrene, R = 2,6-iPr2C6H3 (2a), 2,6-Et2C6H3 (2b), 2,6-Me2C6H3 (2c)], cis-9,10-PhenH2(NR1)(NR2)Ti(OiPr)2 [R1 = 2,6-iPr2C6H3, R2 = 2,6-Et2C6H3 (2d); R1 = 2,6-iPr2C6H3, R2 = 2,6-Me2C6H3 (2e)], and [cis-9,10-PhenH2(NR1)2][o-C6H4(CHNR2)]TiOiPr [R1 = 2,6-iPr2C6H3, R2 = 2,6-Et2C6H3 (3a); R1 = 2,6-iPr2C6H3, 2,6-Me2C6H3 (3b)], have been synthesized from the reactions of TiCl2(OiPr)2 with o-C6H4(CHNR)Li [R = 2,6-iPr2C6H3, 2,6-Et2C6H3, 2,6-Me2C6H3]. The symmetric complexes 2a−2c were obtained from the reactions of TiCl2(OiPr)2 with 2 equiv of the corresponding o-C6H4(CHNR)Li followed by intramolecular C−C bond-forming reductive elimination and oxidative coupling processes, while the asymmetric complexes 2d−2e were formed from the reaction of TiCl2(OiPr)2 with two different types of o-C6H4(CHNR)Li sequentially. The complexes 3a and 3b were also isolated from the reactions for complexes 2d and 2e. All complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of 2a, 2b, 2e, and 3a were determined by X-ray crystallography.