Cationic Ti Complexes with Three [N,O]-Type Tetrazolyl Ligands: Ti↔Fe Transmetalation within Fe Metallascorpionate...

Herein, we report the synthesis of two novel ionic Ti complexes possessing three [N,O]-type bidentate ligands from the reaction of Fe metallascorpionate ligands possessing extended alcohol groups and TiCl₄. The reaction of substituted hydroxyphenyl tetrazole and Fe(ClO₄)₃ in a molar ratio of 3:1 afforded iron scorpionate metalloligands possessing extended arms, which were characterized by IR spectroscopy and ESI-TOF-MS spectrometry. Their molecular structures were also confirmed as neutral Fe-centered scorpionate complexes by X-ray crystallography, in which the extended alcohol groups adopted a tripodal geometry. Moreover, two different crystals of iron scorpionate metalloligand grown from CH₂Cl₂ and CH₃OH were studied, revealing that, in the latter crystal, the tripod arms are folded and aligned toward the C₃-rotational axis of the molecule, whereas the tripod arms are unfolded and spread outward from the rotational axis in the former crystal. These metalloligands are solvatochromatic; a bathochromic shift was observed as the solvent polarity increased. From the reaction, the aforesaid Fe complexes were further reacted with TiCl₄ in a molar ratio of 1:1 to produce ionic [TiL₃]⁺[FeCl₄]^- (L = substituted hydroxyphenyl tetrazole) complexes from the transmetalation of Ti and Fe. The complexes were characterized by various analytical methods including UV/vis and IR spectroscopies, electrospray time-of-flight mass spectrometry (ESI-TOF-MS), and X-ray crystallography.