Catechol derivatives of Group 4 and 5 compounds

The structural modifications of Group 4 and 5 metal alkoxides using the bidentate catechol (C6H3(OH)(2)-1,3 = cat-H-2) have been investigated. From the reaction of [Ti(mu-ONep)(ONeP)(3)](2) (ONep = OCH2CMe3), [Zr(mu-OPri)(ONep)(3) center dot HONep](2)(OPri = OCHMe2), Hf(OEt)(4) (OEt = OCH2Me) with 2 equivalents, and M(OEt)(5) (M = Nb or Ta) with 3 equiv. of cat-H-2 in pyridine (py), the complete removal of alkoxide ligands and isolation of the first neutral catechol derivatives of the Group 4 and 5 species were observed. The corresponding catechol derivatives were structurally characterized as: Ti-3(mu(3)-O)(mu-cat)(3)(cat)(cat-H)(2) (1), Zr-4(mu(4)-O)(mu-cat)(6)(mu-cat-H)(2)(py)(4) (2), Hf-4(mu(4)-O)(mu-cat)(6)(mu-cat-H)(2)(py)(4) (3), M(cat)(2)(cat-H)(py) (M = Nb (4); Ta (5)). Compound 1 is trinuclear with each octahedrally bound metal center having three chelating and three chelating bridging cat ligands, along with a mu(3)-O ligand, to form a corner-missing cube arrangement. Based on charge balance, two of the cat ligands must retain a hydrogen atom (cat-H). The congeners 2 and 3 adopt similar structures wherein each of the metal centers is eight coordinated, adopting a dodecahedral-like geometry. The metals are joined by a mu(4)-O ligand and each cation uses two chelating cat ligands to bridge to two other metal centers as well as coordinating a single py ligand. Again, based on charge balance, two of the ligands must be cat-H ligands. Compounds 1-3 are insoluble at room temperature in their parent solvent. Compounds 4 and 5 are mononuclear wherein each metal center formally adopts a seven coordination capped-trigonal prism involving three chelating catechol ligands, with one being cat-H, along with a coordinated pyridine ligand. Multinuclear NMR data indicate that the structures of 4 and 5 are retained in solution. TGA/DTA data indicated that compound 1 is a reasonable precursor for nanoparticles. 1 was used to generate nanoparticles of TiO2 from benzylalcohol. (c) 2005 Elsevier Ltd. All rights reserved.