Synthesis of new adducts and co-ordination complexes of zirconium and titanium containing β-aminoketone ligands. Crystal structures of isostructural adducts MCl4·2PriHNCMeCHCMeO (M = Ti or Zr) and the complex [Zr(PhNCMeCHCMeO)2Cl2]

Abstract

The reaction of MCl₄ (M = Zr or Ti) with β-aminoketones HL (R¹HNCR²CHCR³O; R² = R³ = Me; R² = Me, R³ = CF₃) yielded the bis(ligand) adducts MCl₄·2HL (M = Zr, R¹ = Prⁱ or Ph; R² = R³ = Me; or R¹ = Prⁱ, R² = Me, R³ = CF₃; M = Ti, R¹ = Prⁱ or CH₂CHCH₂, R² = R³ = Me). Reaction of MCl₄ with the alkali-metal salts of the β-aminoketone ligands yielded the bis(ligand) complexes [M(R¹NCMeCHCMeO)₂Cl₂] (M = Zr, R¹ = Ph, p-ClC₆H₄, p-MeOC₆H₄ or Prⁱ; M = Ti, R¹ = Ph or p-MeOC₆H₄). Crystal structure determinations of the isostructural compounds ZrCl₄·2PrⁱHNCMeCHCMeO and TiCl₄·2PrⁱHNCMeCHCMeO indicated an octahedral co-ordination environment around the metal with the trans monodentate N–O ligands bound through the oxygen only. Strong intramolecular hydrogen bonding of the hydrogen on the nitrogen with the ligand oxygen is consistent with a ligand immonium enolate structure. An X-ray study of the octahedral complex [Zr(PhNCMeCHCMeO)₂Cl₂] indicated that the oxygens of the chelating N–O ligands are trans to each other and the chloride ligands are in a cis arrangement. The plane of one N–O chelate is in the equatorial plane of the complex and the plane of the second N–O ligand is at right angles to the first. The ligand forms a predominantly delocalised chelate ring but some ene–imine structure is apparent.