Reactions of Ti(O-i-Pr)Cl3 with 2-aminophenol and the crystal structure of the zwitterionic complex [Ti(O-i-Pr)Cl3(THF)(-OC6H4NH3+)]•THF

Ti(O-i-Pr)Cl-3 reacts with 1 molar equivalent of 2-aminophenol (HOC6H4NH2) in CH2Cl2 to afford the likely zwitterionic complex [Ti(O-i-Pr) Cl-3(OC6NH3)](2) (1). However, when the reaction is carried out in THF, another zwitterionic complex [Ti(O-i-Pr)-Cl-3(THF) (OC6H4NH3)].(THF) (2) is obtained. With the addition of Ti(O-i-Pr) Cl-3 to a mixture of 2-aminophenol and NEt3 in CH2Cl2, the reaction gives the likely monomeric complex [Ti(O-i-Pr)Cl-3(OC6H4NH2)](-) (HNEt3)(+) (3). The role of the amino group and the effect of the addition of NEt3 and the coordinating THF solvent are discussed. The molecular structure of 2 reveals a species containing the zwitterionic 2-ammonium phenoxide ligand. Two THF molecules are found in the solid state structure in which one THF coordinates to the titanium metal center and the second THF is held tightly via the hydrogen bonding from one ammonium hydrogen. The molecular structure of 2 suggests that the relative bonding abilities of the ligands are in the order of O--i-Pr > -OAr > Cl- > THF. (C) 1998 Elsevier Science S.A. All rights reserved.