Titanium imido complexes containing 1,3,5-triazacyclohexane ligands

The syntheses of the 1,3,5-trimethyl- and tri-tert-butyl-1,3,5-triazacyclohexane-supported imido complexes [M(NR)(R′3tach)Cl2] (M = Ti or Zr (NMR only); R = But or 2,6-C6H3Pri2; R′ = Me or But) are reported, along with that of the thermally robust dibenzyl derivative [Ti(NBut)(Me3tach)(CH2Ph)2]. The tert-butylimido ligand in [Ti(NBut)(Me3tach)Cl2] undergoes exchange with ArNH2 (Ar = 4-C6H4Me or 2,6-C6H4Me or 2,6-C6H3Pri2) to form the corresponding arylimides [Ti(NAr)(Me3tach)Cl2]. The Me3tach ring in [Ti(NR)(Me3tach)Cl2] undergoes slow exchange with But3tach or Me3tacn (1,4,7-trimethyl-1,4,7-triazacyclononane) to give the ring-exchanged products [Ti(NR)(But3tach)Cl2] and [Ti(NR)(Me3tacn)Cl2], respectively. The complexes [Ti(NR)(Me3tach)X2] (R = But or 2,6-C6H3Pri2; X = Cl or CH2Ph) exhibit room-temperature dynamic NMR behaviour via an unusual trigonal twist of the facially coordinated Me3tach ligand, and the activation parameters for these processes have been measured and are discussed. The X-ray structures of [Ti(NR)(But3tach)Cl2] (R = But or 2,6-C6H3Pri2) and [Ti(NBut)(Me3tach)(X)2] [X= Cl or CH2Ph) are reported. Me3tach and But3tach = 1,3,5-trimethyl- and tri-tert-butyl-1,3,5-triazacyclohexane, respectively.