A borate ester represented by one of the following formulae: wherein each R1 is independently hydrocarbyl, a hydrocarbyloxy or a hydrocarbylthio group or both R1 on the same phosphorus atom taken together form a heterocyclic group; each X1 and X2 is independently an oxygen or sulfur; and each R2 is independently a hydrocarbylene group. These reaction products are useful as lubricant additives for oil-based and water-based functional fluids. These materials act as anti-wear, extreme pressure and friction modifying agents.