Direct Synthesis of Titanium Complexes with Chelating cis‐9,10‐Dihydrophenanthrenediamide Ligands through Sequential CC Bond‐Forming Reactions from o‐Metalated Arylimines

Abstract

A series of new titanium(IV) complexes with o-metalated arylimine and/or cis-9,10-dihydrophenanthrenediamide ligands, [o-C(6)H(4)(CH=NR)TiCl(3)] (R=2,6-iPr(2)C(6)H(3) (3 a), 2,6-Me(2)C(6)H(3) (3 b), tBu (3 c)), [cis-9,10-PhenH(2)(NR)(2)TiCl(2)] (PhenH(2)=9,10-dihydrophenanthrene; R=2,6-iPr(2)C(6)H(3) (4 a), 2,6-Me(2)C(6)H(3) (4 b), tBu (4 c)), [{cis-9,10-PhenH(2)(NR)(2)}{o-C(6)H(4)(HC=NR)}TiCl] (R=2,6-iPr(2)C(6)H(3) (5 a), 2,6-Me(2)C(6)H(3) (5 b), tBu (5 c)), have been synthesised from the reactions of TiCl(4) with o-C(6)H(4)(CH=NR)Li (R=2,6-iPr(2)C(6)H(3), 2,6-Me(2)C(6)H(3), tBu). Complexes 4 and 5 were formed unexpectedly from the reactions of TiCl(4) with two or three equivalents of the corresponding o-C(6)H(4)(CH=NR)Li followed by sequential intramolecular C-C bond-forming reductive elimination and oxidative coupling reactions. Attempts to isolate the intermediates, [{o-C(6)H(4)(CH=NR)}(2)TiCl(2)] (2), were unsuccessful. All complexes were characterised by (1)H and (13)C NMR spectroscopy, and the molecular structures of 3 a, 4 a-c, 5 a, and 5 c were determined by X-ray crystallography.