Synthesis and reactivity of titanium(IV)-salen complexes containing oxygen and chloride ligands

The reaction of in situ-generated Ti((OPr)-Pr-i)(2)(X)(2) (X = OAr, OTf) with H(2)salen or H(2)salen* yields the stable, well-characterized Ti(salen)X-2 series of complexes. Ti(salen*)(OTf)(2) could also be synthesized by reacting the previously unknown Ti(salen*)Cl-2 with TMSOTf or AgOTf. The ditriflates could be converted back to the aryloxides upon reaction with 2 equiv of NaOAr. Ti(salen)(4-tert-butyphenoxy)(2) was characterized by X-ray crystallography and found to contain a pseudoplanar salen ligand with two axially coordinated aryloxide ligands. H(2)salen and H(2)salen* were also found to cleanly react with in situ-generated Ti((OPr)-Pr-i)(3)(X) (X = OC(O)R, OTf) to yield the unsymmetrically substituted Ti(salen)((OPr)-Pr-i)(X) and Ti(salen*)((OPr)-Pr-i)(X) complexes, respectively. In the case of X = OTf, the isopropoxide ligand could be cleanly protonated with 4-tert-butylphenol to yield Ti(salen)(OAr)(OTf) in high yield. This complex could also be accessed by the comproportionation reaction of Ti(salen)(OAr)(2) and Ti(salen)(OTf)(2).