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The partial hydrolysis of titanium tetraisopropoxide in the presence of acetylacetone yields the complex [Ti4(μ3-O)2(μ2-OiPr)2(OiPr)8(acac)2] in which [(acac)(OiPr)2TiO(OiPr)Ti(OiPr)2] units are linked into dimers via the bridging oxide ion to form a ladder-like Ti4(μ3-O)2(μ2-OiPr)2 core containing five- and six-coordinate titanium and three-coordinate oxide ions that link the two units together through bonds to the five-coordinate titanium atoms. The Raman spectrum shows bands at 521 and 712 cm-1 that are assigned to ν(Ti−O) modes of bridging isopropoxide ligands and the μ3-oxygen, respectively.

The Fourier transform-infrared (FT-IR) and polarized FT-Raman spectra of titanium tetraisopropoxide (tetraisopropoxytitanium, TPT), in pure and diluted forms, and of 2-propanol have been investigated in conjunction with previous assignments for related compounds to obtain a comprehensive assignment of the vibrational spectra. Evidence was obtained for the presence of both monomeric and associated species of TPT. The latter are formed by coordination expansion through bridging isopropoxy ligands. For both monomeric and associated TPT species, vibrational modes of isopropoxy ligands with nu(C-O) mode character were coupled to nu(s)(Ti-O) and nu(as)(Ti-O) modes (interligand coupling). The symmetrically coupled ligand modes gave rise to intense, strongly polarized bands in the Raman spectrum. The antisymmetrically coupled ligand modes gave rise to strong bands in the IR spectrum at lower wavenumbers than the corresponding Raman bands. Molecular association of TPT produced negligible shifts in the ligand modes coupled to the nu(s)(Ti-O) mode in the Raman spectrum. In contrast, the degeneracy of the strong ligand modes coupled to the nu(as)(Ti-O) mode was lifted upon molecular association, yielding band shifts and splittings in the IR spectrum of neat TPT.