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]

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)2L}n] (RO = isopropoxo, (1R,2S,5R)-(−)-menthoxo) (6–11) and [{(Ti(O–i-Pr)3)3L}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-dihydroxy-5,6-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.