We quantified the decomposition kinetics of group 4 metal isopropoxides by monitoring the reaction via 1 H NMR. Under identical conditions, titanium reacts an order of magnitude faster than zirconium, and hafnium is slightly slower than zirconium. In the case of titania, the reaction follows an S N 1 mechanism and the addition of TOPO accelerates the reaction by stabilizing the positive charge in the transition state. When the ratio of chloride to isopropoxide was varied in the precursor series TiCl