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.

Graphical abstractTitanocene 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 full-size imageDownload as PowerPoint slide