A family of titanium (IV) alkoxo complexes with N,O and O,O chelating ligands. Crystal structure of [Ti(O-i-Pr)(2){2-(-)-menthoxo-pyridine}(2)]

摘要

In view of the wide applicability and versatility of titanium based Lewis acids in selective organic synthesis including asymmetric synthesis, we have synthesized a family of mono and polyatomic titanium derivatives. The polymetallic complexes prepared are bridged by pyridimine, quinone and triazine based ligands. The synthesis of [{Ti(O-i-Pr)(3)(Oddbf)}(2)] (1), [Ti(O-i-Pr)(2)(Oddbf)(2)] (2), [{Ti(O-i-Pr)(2)-(Oddbf)(OMent)}(2)] (3) (ddbfO = 2,3-dihydro-2,2-dimethyl-benzofuranoxo; MentO = (1R,2S,5R)-(-)-menthoxo), [{Ti(O-i-Pr)(3)(OMenpy)}(2)] (4), [Ti(O-i-Pr)(2)(OMenpy)2] (5) (MenpyO = (1S,2S,5R)-(-)-menthoxo-pyridine); [{(Ti(OR)(3))(2)L}] (RO = isopropoxo, (1R,2S,5R)-(-)-menthoxo) (6-11) and [{(Ti(O-i-Pr)(3))(3)L}(n)] (12) was accomplished from a Lewis acid such as Ti(O-i-Pr)4, [{Ti(O-i-Pr)(3)(OMent)}(2)] or [Ti(OMent)4] and chelating ligands (ddbfOH = 2,3-dihydro-2,2-dimethyl-benzofuranol; MenpyOH = (1R,2S,5R)-(-)-5-methyl-2-isopropyl-1-(2'-pyridinyl)cyclohexan-1-ol; LH2 = 4,6-dihydroxy-2,5-diphenyl-pyrimidine, 2,4-dihydroxy5,6-dimethyl-pyrimidine, 5,8-dihydroxy-1,4-napthoquinone, 2,5-dihydroxy-1,4-benzoquinone and LH3 = cyanuric acid) that provide a rigid framework for the metal centre. The molecular structure of 5 has been determined by single crystal X-ray diffraction studies. (c) 2006 Elsevier B.V. All rights reserved.