Synthesis and structure of chiral Titanium(IV) complexes containing N-substituted amino alcohols

摘要

Several Ti(IV)-amino alcohol complexes of the type TiX2[OCHPhCHPhnN(R)] (X = NMe2, NEt2, (OPr)-Pr-i; R = SO2CF3 (Tf), SO2Ar, CH2Ar) have been synthesized by protonolysis of Ti(NMe2)(4), Ti(NEt2)(4), or Ti((OPr)-Pr-i)(4) with various N-substituted amino alcohol ligands derived from (1S,2R)-(+)-2-amino-1,2-diphenylethanol. X-ray crystal structures of [Ti[OCHPhCHPhN(Tf)](NMe2)(2)](2) (2a), [Ti[OCHPhCHPhN(CH2[2,4,6-(CH3)(3)C6H2])(NMe2)(2)](2) (2d), and [Ti[OCHPhCMPhN(Tf)]((OPr)-Pr-i)(2)](2) (4) show these compounds to be dimericin the solid state, bridging through the amino alcohol oxygens; vapor pressure osmometry (VPO) molecular weight measurements on 2-4 confirm a dimeric solution structure, The dimers [Ti[OCHPhCHPhN(Tf)](NEt2)(2)](2) (3) and 4 form 4-(dimethylamino)pyridine (DMAP) adducts which exhibit a concentration-dependent monomer-dimer equilibrium by VPO. An X-ray crystal structure of Ti[OCHPhCHPhN(Tf)]((OPr)-Pr-i)(2)[DMAP] (6), however, indicates that it is monomeric in the solid state. [References: 50]