Synthesis and Molecular Structures of Some New Titanium(IV) Aryloxides

Abstract

The coordination chemistry of model phenolic ligands (pyrocatechol, salicylic acid, and 2,2'-biphenol) that are able to form respectively five-, six-, or seven-membered rings with titanium(IV) alkoxides is investigated. With pyrocatechol, a polynuclear complex containing 10 Ti atoms was characterized with a not very common doubly bridging mu3-(O,O,O',O') coordination mode. With salicylic acid, a monomeric tris(chelate) complex was obtained. With 2,2'-biphenol, a polynuclear complex containing six Ti atoms was obtained showing both mu2-(O,O') and mu2-(O,O,O') coordination modes for the ligands. Intermolecular interactions in the solid state for these three new compounds are also quantitatively discussed using the partial charge model.

A Tetrameric Titanium Alkoxide as a Lactide Polymerization Catalyst

“…Many known multinuclear titanium complexes contain more than one type of alkoxy or aryloxy group (e. g., OR and OR9 or OAr and OAr9) in their structures. [13] Secondly, 1 is readily soluble in toluene, a solvent commonly used in LA polymerization, whereas many homoleptic compounds of the type Ti x (OR) y [14] and oxo-bridged alkoxides of the type Ti x O y (OR) z [15] exhibit poor solubility in standard organic solvents. Third, 1 is stable in the solid state and in toluene at ambient temperature over an extended period of time, although it is thermally unstable in toluene at elevated temperatures.…”

“…1 H and 13 C{ 1 H} spectra were recorded at ambient temperature on a Varian VXR-400 NMR spectrometer using standard parameters. The chemical shifts are referenced to the residual peaks of CDCl 3 (7.24 ppm, 1 H NMR; 77.0 ppm, 13 C{ 1 H} NMR). Elemental analyses were performed by Desert Analytics Laboratory.…”

Nonempirical Quantification of Molecular Interactions in Supramolecular Assemblies

“…For a system with N electrons, it may be shown that Equation (2) implies the existence of a common electronic chemical potential m e constant from orbital to orbital, Equation (7). [13] …”

Thermodynamics of Hydrogen Bond Patterns in Supramolecular Assemblies of Water Molecules

“…A good example is provided by a neutral tris-chelate titanium(IV) complex recently synthesized in our laboratory. [23] Due to the extremely short O ¥¥¥ O distances (250 and 255 pm between butanol and salicylic acid molecules) and to the presence of a strong positive charge, q(Ti) % 3, in the neighborhood of the hydrogen bridges, it seemed that we had good evidence for a rather strong hydrogen bond. This was indeed the case, as the value derived from the optimized hydrogen bond pattern (Figure 12 a) was found to be E HB À 23.2 AE 0.1 kJ mol À1 .…”