POLYOXOTITANATES JOIN THE KEGGIN FAMILY - SYNTHESIS, STRUCTURE AND REACTIVITY OF [TI18O28H][OBU(T)](17)

Reaction of Ti(OBu(t))(4) with about 1 equivalent of water in tert-but yl alcohol for 5 d at 100 degrees C yielded the polytitanate complex [ Ti18O28H][OBu(t)](17). A single-crystal X-ray diffraction study of its Bu(1)OH solvate [a = 15.789(4), b = 29.544(5), c = 27.496(5) Angstrom , beta = 91.85(5)degrees; Z = 4; space group P2(1)/c-C-2h(5)] revealed a Ti18O45 metal-oxygen framework having a pentacapped Keggin structur e, i.e. a Ti13O40 Keggin unit capped by five TiO moieties which lie ab ove five of the six approximately square faces of the T-d-distorted cu boctahedron defined by the metals in the Keggin unit. All seventeen of the terminal oxygen atoms are bonded to tert-butyl groups. This compl ex is the most highly condensed titanium alkoxide hydrolysis product i solated to date and showed good stability in solution, retaining its s tructure and showing no decomposition after 24 h at ambient temperatur e in toluene-tert-butyl alcohol solution, according to NMR spectroscop y. Reactions of the complex with water, 2-methylbutan-2-ol and triethy lamine are also reported.