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Six crystalline titanodiphenylsiloxanes have been synthesised by reaction of diphenylsilanediol (DPSD) with titanium tetraisopropoxide or its complexes with acetylacetonate (acac) as ligand. Two of them show a spirocyclic structure with the formula TiO2 [O2Si2(C6H5)4 ]2A and TiO2 [O4Si4(C6H5)8 ]2B which have already been described in the literature. Two compounds C and D were identified by X-ray analysis to have the same bicyclic structure but different coordinating solvent molecules. Tetrahydrofuran acts as a non-bridging ligand at the Ti atoms in [Ti(acac)O1.5 ]2 [OSi(C6H5)2 ]3 ·2C4H8O C while dioxane acts as a bridging ligand between the Ti atoms of neighbouring molecules of [Ti(acac)O1.5 ]2 [OSi(C6H5)2 ]3 ·3C4H8O2D. The titanodiphenylsiloxanes E and F were identified by a cyclotetrameric structure and the formulas [Ti(acac)2O]2 [OSi(C6H5)2 ]2 and [Ti(acac)2O][OSi(C6H5)2 ]3 , respectively. The titanodiphenylsiloxanes A–E were characterised by 29Si and 17O NMR spectroscopy, IR and time-of-flight mass spectrometry measurements. The hydrolytic stabilities of the Si–O–Ti bonds in the titanodiphenylsiloxanes A–E have been examined mainly by means of 29Si NMR spectroscopy. The results reveal a strong influence of the structure type of the titanodiphenylsiloxanes on the hydrolytic stability of their Si–O–Ti bonds apart from the hydrolytic conditions (amount of water, Si, Ti and H+ concentration). The hydrolytic stability of the titanodiphenylsiloxanes A–E decreases in the order cyclotetramer (E)>spirocyclo (A, B)>bicyclo (C, D). Reasons for the different hydrolytic stability are discussed. The results on the different hydrolytic stabilities of Si–O–Ti bonds can contribute to a better understanding of the synthesis of homogeneous heterometal materials on a molecular scale via the sol–gel process.

X-Ray and NMR spectroscopic characterisation of cyclic titanodiphenylsiloxanes and examination of the hydrolytic stability of their Si–O–Ti bonds