Organotitanium phosphates with free P–OH groups: Synthesis, spectroscopy and solid state structures

• Role of titanium source in determining the structural type of resultant titanophosphate is demonstrated.
• A titanophosphate with chiral helical superstructures is isolated and characterized.
• A discrete tetranuclear titanophosphate cluster which is held together by eight phosphonate ligands is reported.
• A mechanism for the formation of the tetranuclear titanophosphate cluster is proposed.

Titanocene dichloride reacts with 2,6-diisopropylphenyl phosphate (dippH2) in tetrahydrofuran to yield a functionalized mononuclear titanium phosphate molecule [Cp2Ti(dippH)2] (1) in 70% yield. A similar reaction with titanium bis(acetylacetonate)diisopropoxide [Ti(acac)2(OiPr)2] yields a tetranuclear cluster [Ti4(μ2-OH)2(OiPr)2(dipp)4(dippH)4(THF)2] (2) in 70% yield. Owing to the presence of free P–OH groups in 1, its reactivity towards aluminum alkyls has been investigated. Compounds 1 and 2 have been characterized with the aid of elemental analysis, mass, IR and NMR (1H and 31P) spectroscopy. In spite of the poor quality of the crystals obtained, the solid-state structures of compounds 1 and 2 have been determined by single crystal X-ray diffraction studies to a satisfactory level. Compound 1 crystallizes as hydrogen bonded chiral helical superstructures in the monoclinic non-centrosymmetric P21 space group. Compound 2 is a discrete tetranuclear titanophosphate cluster which is held together by eight phosphate ligands.

Titanocene dichloride reacts with 2,6-diisopropylphenyl phosphate (dippH2) in tetrahydrofuran to yield a mononuclear titanium phosphate molecule [Cp2Ti(dippH)2] which forms a left handed helical polymer as a result of PO⋯HO–P interactions between the neighboring phosphate ligands. A similar reaction with [Ti(acac)2(OiPr)2] yields a tetranuclear cluster [Ti4(μ2-OH)2(OiPr)2(dipp)4(dippH)4(THF)2].Figure optionsDownload as PowerPoint slide