Data underlying the figures in the publication "Mechanistic Insight into the Precursor Chemistry of ZrO2 and HfO2 Nanocrystals; towards Size-Tunable Syntheses" publish in JACS Au: https://doi.org/10.1021/jacsau.1c00568 Table of contents: The .pxp documents contain the experimental data of the figures in the manuscript and they can be opened/edited with the software IGOR Pro 8.0 or higher. 1. Figure 1.pxp. (A) Scheme for the reaction of ZrCl4.2THF with TOPO. (B) 1H NMR of the titration of a solution of 0.05 M ZrCl4.2THF in CDCl3 with increasing equivalents of TOPO. The latter is added as a 0.5 M solution, gradually diluting the zirconium complex. (C) 31P NMR of the same titration. The spectrum for 0.2 equivalents was amplified twofold to observe the resonances more clearly. The spectra have a relative x-offset of 1 ppm with respect to each other. (D) The different TOPO species over the course of the titration. The total amount of Zr in the sample was 25 μmol. 2. Figure 3.pxp. (A) Scheme for the reaction of Zr(OiPr)4.iPrOH with TOPO. (B) 1H NMR of the titration of a solution of 0.05 M Zr(OiPr)4.iPrOH in CDCl3 with increasing equivalents of TOPO relative to Zr. TOPO is added as a 0.5 M solution, gradually diluting the zirconium complex. The total amount of Zr in the sample was 25 μmol. 3. Figure 4.pxp. (A) Reaction scheme for the titration of a 1 : 1 mixture of ZrCl4 : Zr(OiPr)4.iPrOH with TOPO in C6D6 at room temperature. (B) The 31P NMR spectra of the titration. The ratio of Zr to TOPO is indicated in the figure. 4. Figure 5.pxp. 1H and 31P NMR of the reaction mixture with 1 equivalent of ZrCl4 in C6D6. Aliquots were taken at different temperatures during the ramp and at different times at the final reaction temperature of 340 °C. 5. Figure 6.pxp. (A) X-Ray PDFs (acquired at 80 °C to melt TOPO) of reaction mixtures heated to different temperatures as indicated. The range of distances as determined from the DFT optimized structures of (5) and (6) are indicated by the grey zones. (B) PDF refinement for the reaction product at 340 °C after 90 min, using a dual-phase model with the tetragonal zirconia (P42/nmc) and the DFT optimized ZrCl4.2TPPO complex (2). 6. Figure 7.pxp. (A) Concentration of various intermediates at different times at the final reaction temperature of 340 °C for a 1:1 mixture of ZrCl4 : Zr(OiPr)4.iPrOH. The concentration of different species is calculated corresponding to the integrals of TOPO bound to the Zr-centers in 31P NMR. (B) Normalized, relative concentration of propene and isopropyl chloride in the reaction headspace at different temperature/time points. 7. Figure 8.pxp. (A) Scheme showing the Zr(OiPr)4.iPrOH injection strategy to increase particle size and yield. (B) TEM and histogram of particles before and after each injection. The average size is indicated. (C) PDF fit for the purified product after three injections with the tetragonal zirconia (P42/nmc) model. The refined crystallite diameter is 5.33 nm.