Having observed formation of the desired product, we set out to optimize the hydride reagent. An initial survey of hydride sources at stoichiometric loading (H:P = 1:1) showed that potassium hydride (KH) gave superior results to other common hydride reagents in regard to conversion of phosphate input and yield of phosphite (Tables and). The lower lattice energy of KH likely contributes to its higher reactivity at the crystal surface. On account of the higher yields obtained using KH, we chose to use it as the hydride source to continue our study. Use of KH as the reduc-tant also avoided the accumulation of phosphorylated phosphite (isohypophosphate, [O2HP-OPO3] 3-) 51-54 which was formed using other hydride reagents.