Structurally Diverse Aggregating Condensations of Ti(IV) Catecholates

The simple 1:1 reaction of naphthalene-2,3-diol (H2Np) with Ti(OiPr)4 has a complicated outcome, one rich in
diversity and elucidated in this paper by X-ray crystallography and NMR spectroscopy. The reaction in CDCl3
produces a crystalline precipitate, which was found to be the symmetrical dimer [TiNp(OiPr)2]2(HOiPr)2 whose
coordinated HOiPr units are hydrogen bonded to OiPr groups (A). A second crystal was also harvested and found
to be a partially hydrolyzed 6:6 assembly [Ti3(μ3-O)(μ-Np)2(Np)(μ-OiPr)(OiPr)(HOiPr)2(μ-O)]2 (B) constructed of
μ-oxo-linked inverted halves, each a 3:3 assembly anchored by a μ3-oxo group. The supernatant was deduced to
contain a soluble 3:3 product [TiNp(OiPr)2]3(HOiPr) possessing the same stereochemistry as B and its likely hydrolysis
precursor. When A was redissolved, it produced what appeared to be a 4:4 condensation product, which was also
present in the supernatant when the reaction was conducted in the presence of HOiPr-absorbing 13X molecular
sieves, or when the reaction mixture was heated. In an analogous reaction, Ti(OtBu)4 produced only an A-like
dimeric product possessing pentacoordinate metal centers.